Seminars this semester


   Series:

 
Jan 29 Wed K.S.Williams (Carleton, Ottawa)
16:00 Continued fractions and Eisenstein's problem
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Feb 19 Wed M.M.Dodson (York)
16:00 Covers, $s$-lengths and order
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Feb 26 Wed Peter Kropholler (QMW)
16:00 Bounded cohomology
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Mar 4 Wed David Jordan (Sheffield)
16:00 Iterations of automorphisms and representations of rings
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Mar 18 Wed John Greenlees (Sheffield)
16:00 Groups and spheres
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May 6 Wed P.Gruber (Vienna)
16:00 Modern and classical aspects of the geometry of numbers
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May 20 Wed E.Kappos (Sheffield)
16:00 Dynamical systems approach to nonlinear control theory
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Jun 24 Wed T.Lau (Alberta)
16:00 Invariant subalgebras and subgroups of locally compact groups
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Oct 14 Wed A.Sudbery (York)
16:00 Quantum groups
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Oct 28 Wed Victor Bryant (Sheffield)
16:00 Two interesting matroid problems
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Nov 11 Wed Richard Pinch (Cambridge)
16:00 Pseudoprimes and Carmichael numbers
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Nov 25 Wed C.A.McGibbon (Wayne State)
16:00 Algebraic limits and infinite dimensional spaces
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Dec 2 Wed Martin Holland (Sheffield)
16:00 Differential operators, curve singularities and finite dimensional algebras
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Jan 20 Wed K.A.Brown (Glasgow)
16:00 What is a quantum group?
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Feb 3 Wed B.D.Mestel (Exeter)
16:00 An application of dynamical systems theory to adaptive control
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Feb 17 Wed A.J.Granville (Georgia)
16:00 Primality testing and Carmichael numbers
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Feb 24 Wed David Benson (Oxford)
16:00 Primality testing and Carmichael numbers
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Mar 10 Wed M.Brodmann (Z)
16:00 Bounds for the cohomology of projective varieties
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Mar 16 Tue V.Lyubashenko (York)
16:00 Algebra of functions on a quantum group at a root of unity
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May 19 Wed Peter Dixon (Sheffield)
16:00 Varieties of Banach algebras
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May 26 Wed M.Herrmann (K)
16:00 On the blowing-up of powers of ideals
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May 26 Wed N.V.Trung (Hanoi)
16:00 Criteria for Gorenstein Rees algebras
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Oct 20 Wed C.J.H.MacDiarmid (Oxford)
16:00 Age-dependent branching processes; recent improved estimates
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Oct 27 Wed D.Burns (KCL)
16:00 Adams operations, cannabalistic classes and integral representations
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Nov 17 Wed Shaun Bullett (QMW)
16:00 Mating quadratic maps with the modular group
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Dec 1 Wed Bruce Westbury (Nottingham)
16:00 State sum model invariants of 3-manifolds
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Feb 2 Wed David Mond (Warwick)
16:00 The geometry of free divisors
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Feb 9 Wed Ronnie Brown (Bangor)
16:00 Holonomy, foliations and groupoids
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Feb 16 Wed Jeremy Rickard (Bristol)
16:00 What could be simpler than the trivial module?
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Mar 9 Wed M.P.Brodmann (Z)
16:00 Blowing-ups and their visualisation by computer
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Mar 9 Wed T.Albu (Bucharest and Glasgow)
16:00 Krull dimension, dual Krull dimension, and the Hopkins-Levitzki theorem
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Mar 16 Wed L.Beineke (Purdue and Oxford)
16:00 A survey of graph decompositions
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May 4 Wed D.Strauss (Hull)
16:00 The semigroup $\beta\mathbb{N}$
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Jun 2 Thu Andy Baker (Glasgow)
16:00 Vertex operators in algebraic topology
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Jun 2 Thu Neil Strickland (MIT)
16:00 Isogenies and Dyer-Lashof operations in $E_n$-theory
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Oct 4 Tue P.Polo (Pierre et Marie Curie, CNRS)
16:00 K-theory of twisted differential operators on complete homogeneous spaces
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Oct 5 Wed T.Bridgeman (Liverpool)
16:00 The marking of examination papers
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Oct 19 Wed M.V.Karasev (Moscow)
16:00 Noncommutative products of functions defined by ``membranes'' and ``strings''
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Oct 26 Wed M.Hirsch (Berkeley)
16:00 Fixed points of monotone mappings
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Nov 2 Wed P.J.Rippon (OU)
16:00 On the boundary of certain Siegel discs
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Nov 9 Wed A.King (Liverpool)
16:00 The cohomology rings of moduli spaces
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Nov 23 Wed J.Cremona (Exeter)
16:00 The arithmetic of elliptic curves
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Jan 11 Wed G.R.Robinson (Leicester)
16:00 On eigenvalues of elements of finite linear groups
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Feb 22 Wed Karen Smith (MIT)
16:00 Prime characteristic techniques in the study of algebraic varieties over the complex numbers
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Mar 1 Wed Y.Kosman-Schwarzbach (Paris)
16:00 Poisson geometry and odd Poisson brackets
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Mar 8 Wed L.Avramov (Purdue)
16:00 Hilbert series and Laurent coefficients of graded modules
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Mar 9 Thu L.Avramov (Purdue)
16:00 L.c.i. homomorphisms and vanishing of André-Quillen homology
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May 10 Wed T.Thompson (Dalhousie)
16:00 When are soap bubbles spheres? -- an excursion into other normed spaces
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May 15 Mon T.Bier (Ulm)
16:00 Existence and nonexistence of magic structures
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May 17 Wed Grant Walker (Manchester)
16:00 Modular analogues of classical symmetric functions
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May 24 Wed M.Cannell (George Green Memorial Fund)
16:00 George Green, mathematician and physicist, 1793--1840; the background to his life and work
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May 31 Wed I.Anderson (Glasgow)
16:00 Remarkable revelations concerning Kirkman's schoolgirls
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Oct 4 Wed D.Woodcock (QMW)
16:00 The partition algebra as a `deformation' of the Schur algebra
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Oct 11 Wed C.M.Wood (York)
16:00 Energy in geometry
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Oct 18 Wed R.J.Sharp (Manchester)
16:00 Zeta functions, closed geodesics and periodic orbits of dynamical systems
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Oct 25 Wed E.C.Lance (Leeds)
16:00 Compact quantum groups
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Nov 1 Wed K.M.Ball (UCL)
16:00 The reverse isoperimetric problem
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Nov 8 Wed Jeremy Gunawardena (Hewlett-Packard)
16:00 Dynamics of nonexpansive maps
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Nov 15 Wed John Greenlees (Sheffield)
16:00 Algebraic shadows of equivariant topology
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Nov 29 Wed H.Petzl (Utrecht)
16:00 Cousin complexes and flat ring extensions
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Dec 6 Wed Bill Crawley-Boevey (Leeds)
16:00 General representations of quivers
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Jan 31 Wed K.Mischaikow (Georgia Institute of Technology)
16:00 Chaotic dynamics and the Conley index
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Feb 13 Tue M.Brodmann (Z)
16:00 A survey of local cohomology and connectivity in algebraic varieties
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Feb 21 Wed E.J.Beggs (Swansea)
16:00 Soliton interactions in the principal chiral model
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Feb 28 Wed K.Erdmann (Oxford)
16:00 Representations of general linear groups and symmetric groups
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Mar 4 Mon C.Le Merdy (France-Comte)
16:00 Operator algebra structures on commutative and noncommutative $\ell^p$
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Apr 24 Wed Reg Wood (Manchester)
16:00 Differential operators and the Steenrod algebra
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May 8 Wed D.Salomon (Warwick)
16:00 Floer homology and the general Arnold conjecture
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May 15 Wed S.M.Rees (Liverpool)
16:00 Some new examples of convergence groups
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May 22 Wed T.Bier (Sheffield)
16:00 Permutations and posets
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Aug 21 Wed M.Filali (Oulu)
16:00 On the semigroup $\beta$S and some applications
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Oct 9 Wed Victor Flynn (Liverpool)
16:00 Rational points on curves
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Oct 23 Wed J.Roberts (Edinburgh)
16:00 Moduli spaces of flow graphs and 3-manifold invariants
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Oct 30 Wed David Mond (Warwick)
16:00 Families of free divisors
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Nov 12 Tue Y.V.Selivanov (Moscow)
16:00 Biprojective topological algebras
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Nov 20 Wed Ronnie Brown (Bangor)
16:00 A non-abelian tensor product of groups
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Nov 27 Wed J.C.McConnell (Leeds)
16:00 Effective calculation -- first steps in Gröbner bases
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Dec 11 Wed A.K.Austin (Sheffield)
16:00 Mathematical proof -- what shall we tell the students?
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Jan 29 Wed A.S.Dzhumadil'daev (Alma-Ata)
16:00 Lie algebroids, cohomologies and noncommutative Lie algebras
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Feb 26 Wed R.Marsh (Glasgow)
16:00 Quantum groups and canonical bases
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Mar 5 Wed Roger Webster (Sheffield)
16:00 Log-convex solutions to $f(x+1)=g(x)f(x)$ -- $;amma$-type functions
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Apr 16 Wed V.Goryunov (Liverpool)
16:00 Plane curves and Legendrian knots
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Apr 23 Wed J.F.McKee (Edinburgh)
16:00 Factoring on a desert island
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May 7 Wed F.Vivaldi (QMW)
16:00 Discrete dynamics and algebraic numbers
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May 7 Wed P.Shiu (Loughborough)
16:00 A remarkable function from Diophantine Approximations (the devil's staircase and an angel's ladder)
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May 14 Wed A.West (Leeds)
16:00 Surfaces which do not intersect their focal set
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May 21 Wed Jon Carlson (Athens)
16:00 Computers, polynomial rings and group cohomology
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Jun 2 Mon Peter May (Chicago)
16:00 Equivariant topology and nonequivariant applications
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Oct 21 Wed John Hunton (Leicester)
16:00 Quasi-periodic tilings and homotopy theory
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Oct 28 Wed A.J.Power (Edinburgh)
16:00 Higher dimensional categories
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Nov 11 Wed I.Gordon (Edinburgh)
16:00 Representations of quantum groups at roots of unity
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Nov 25 Wed Kevin Buzzard (Imperial)
16:00 Artin's conjecture on L-functions
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Dec 2 Wed Niall Mackay (Sheffield)
16:00 Yangians and Dorey's rule
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Dec 9 Wed W.W.Wheeler (Leicester)
16:00 Infinite dimensional modules for finite groups
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Jan 20 Wed Kirill Mackenzie (Sheffield)
16:00 Notions of double
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Feb 3 Wed S.Merkulov (Glasgow)
16:00 Strong homotopy and Gerstenhaber-Batalin-Vilkovoski algebras of a Kähler manifold
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Feb 17 Wed M.Weber (Dresden)
16:00 On finite elements in vector lattices
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Mar 3 Wed P.Shiu (Loughborough)
16:00 Problems on sums of two squares
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Mar 10 Wed G.A.Jones (Southampton)
16:00 Dessins d'enfant: geometric actions of Galois groups
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Apr 28 Wed J.C.Robson (Leeds)
16:00 Dedekind-like noncommutative rings
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May 12 Wed I.R.Porteous (Liverpool)
16:00 Robust features of surfaces in $\mathbb{R}^3$
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May 19 Wed Burt Totaro (Cambridge)
16:00 Singular algebraic varieties and elliptic cohomology
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May 26 Wed K.A.Brown (Glasgow)
16:00 Some current themes in representation theory
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Oct 13 Wed Michael Weiss (Aberdeen)
16:00 Homotopy theoretic analysis of spaces of smooth embeddings
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Oct 20 Wed R.Green (Lancaster)
16:00 Quantum algebras at $v=\infty$
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Nov 3 Wed Srikanth Iyengar (Sheffield)
16:00 Intersection theorems in commutative algebra
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Nov 17 Wed A.Borovik (UMIST)
16:00 Probabilistic recognition of black box groups
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Nov 24 Wed John Pym (Sheffield)
16:00 The Ellis semigroup of the action of a connected semisimple Lie group on a maximal compact subgroup
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Dec 8 Wed Ulrike Tillmann (Oxford)
16:00 Moduli spaces of Riemann surfaces and CFT
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Dec 15 Wed H.Hauer (Nottingham)
16:00 Generalised Riemann-Roch formulas
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Feb 9 Wed Susan Howson (Nottingham)
16:00 Non-Abelian Iwasawa theory and applications to elliptic curves
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Feb 16 Wed M.Brodmann (Z)
16:00 Associated primes of local cohomology modules
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Feb 18 Fri Larry Smith (G)
16:00 Coinvariants, Jacobians and Poincaré duality
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Mar 1 Wed Ronnie Brown (Bangor)
16:00 Non-abelian methods for computing modules of identities among relations for presentations of groups: crossed complexes
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Mar 15 Wed A.Henke (Kassel)
16:00 The Sierprinski gasket, representations and the symmetric group
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Mar 22 Wed Ian Grojnowski (Cambridge)
16:00 Rigid structure and the symmetric group
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Apr 5 Wed Y.Kosmann-Schwarzbach (Ecole Polytechnique)
16:00 Poisson homogeneous spaces
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May 3 Wed Moty Katzman (Sheffield)
16:00 Edge algebras which are complete intersections
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May 10 Wed Ran Levi (Aberdeen)
16:00 The spaces of equivalences between $p$-completed classifying spaces
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May 22 Mon K.Mischaikow (Georgia Institute of Technology)
16:00 Rigorous computation of low-dimensional dynamics and the combinatorial geometry of flows
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Sep 27 Wed A.Frankild (Copenhagen)
16:00 Vanishing of local homology and some applications
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Oct 2 Mon J.Br (Stuttgart)
16:00 Almost periodic sequences. binary additive problems and the circle method
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Oct 11 Wed Roger Plymen (Manchester)
16:00 The Baum-Connes conjecture and the local Langlands conjecture for GL(n): are they related?
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Oct 17 Tue P.Jorgensen (Copenhagen)
16:00 Spectra of modules
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Oct 18 Wed P.Covey-Crump (GCHQ)
16:00 Campanology and mathematics
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Nov 1 Wed H.Khudaverdyan (visiting UMIST)
16:00 Batalin-Vilkovisky formalism geometry and semidensities of odd symplectic manifolds
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Nov 15 Wed Hellen Colman (Sheffield)
16:00 LS-category of compact Hausdorff foliations
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Nov 22 Wed S.Hurder (Chicago)
16:00 Foliations: at the crossroads of geometry and topology
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Nov 22 Wed Imre Leader (Cambridge)
16:00 Set systems with few disjoint pairs
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Nov 29 Wed J.Cremona (Nottingham)
16:00 Reduction of binary forms--how to find small equations for hyperelliptic curves
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Dec 6 Wed David Jordan (Sheffield)
16:00 Rings generated by Eulerian derivatives
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Dec 13 Wed A.Wilkie (Oxford)
16:00 Tame topology and O-minimal structures
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Feb 7 Wed S.Koenig (Leicester)
16:00 Schur-Weyl duality and dominant dimension
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Feb 14 Wed Vladimir Bavula (Sheffield)
16:00 Holonomic D-modules, the Dixmier problem and the Jacobian conjecture
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Feb 28 Wed A.Volovikov (Steklov, visiting Liverpool)
16:00 Indexes of G-spaces
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Mar 7 Wed V.Nikulin (Liverpool)
16:00 A theory of Lorenzian (or hyperbolic) Kac-Moody algebras
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Mar 13 Tue Matthew Ando (Urbana)
16:00 Equivariant elliptic cohomology of spin bundles
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Mar 14 Wed Alan Camina (UEA)
16:00 Sizes of conjugacy classes - what do they tell us about the structure of finite groups?
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Mar 20 Tue W.Timmermann (Dresden)
16:00 Mathematical structures in quantum physics - some historical remarks
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Mar 21 Wed B.Zilber (Oxford)
16:00 Logic and Schanuel-type conjectures
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Mar 28 Wed S.Galbraith (Bristol)
16:00 Abelian varieties and cryptography
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Apr 4 Wed Andrew Pressley (KCL)
16:00 Representations of quantum affine algebras
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May 2 Wed Charles Thomas (Cambridge)
16:00 Geometric structures on fake projective and lens spaces
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May 9 Wed John Greenlees (Sheffield)
16:00 Old and new dualities in algebra and topology
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May 16 Wed Marian Anton (Sheffield)
16:00 Undetected general linear group cohomology
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May 17 Thu H.-B.Foxby (Copenhagen)
16:00 Properties of homomorphisms in commutative algebra
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Oct 3 Wed S.Donkin (QMW)
16:00 Some remarks on cohomology of line bundles on flag varieties
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Oct 10 Wed B.Koeck (Southampton)
16:00 Computing the homology of Koszul and Dold-Puppe complexes
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Oct 17 Wed M.Mackaay (Nottingham)
16:00 Categorical groups in differential geometry and 4-dimensional geometry
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Oct 24 Wed Ieke Moerdijk (Utrecht)
16:00 Models for the leaf spaces of a foliation
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Nov 7 Wed G.Robinson (Birmingham)
16:00 Local structure and blocks
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Nov 13 Tue M.Brodmann (Z)
16:00 Bounding sheaf cohomology by the diagonal
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Nov 14 Wed J.Keating (Bristol)
16:00 Random matrix theory and $\zeta(1/2+it)$
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Nov 20 Tue R.Hill (UCL)
16:00 The Kubota symbol on $SL_n$
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Nov 26 Mon K.Mischaikow (Georgia Institute of Technology)
16:00 Searching for holes and volumes: biomedical imaging and computational topology
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Dec 5 Wed Frank Neumann (Leicester)
16:00 Etale homotopy and moduli of stacks
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Dec 12 Wed Imma Galvez (Sheffield)
16:00 Elliptic genera and invariants of manifolds with boundary
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Dec 19 Wed Rachel Camina (Cambridge)
16:00 Linearity of pro-p-groups
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Feb 12 Tue Angus MacIntyre (University of Edinburgh)
16:00 Connections between Schanuel's Conjecture and Logic.
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Feb 13 Wed M.Gross (Warwick)
16:00 Topological mirror symmetry
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Feb 19 Tue Johannes Kellendonk (University of Cardiff)
16:00 Topological aspects of aperiodic ordered systems.
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Feb 20 Wed Alan Camina (Sheffield)
16:00 Pro-$p$-groups of finite width
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Feb 26 Tue Aidan Schofield (University of Bristol)
16:00 Noncommutative moduli spaces of vector bundles
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Feb 27 Wed Ian Stewart (Leicester)
16:00 Finite model theory, complexity theory and program schemes (The MathFIT initiative)
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Mar 5 Tue Tom Lenagan (University of Edinburgh)
16:00 Noncommutative Dehomogenisation
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Mar 6 Wed C.Cocks (GCHQ)
16:00 Recent developments in identifier-based public key cryptosystems
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Mar 13 Wed Greg Sankaran (Bath)
16:00 Nef divisors in the moduli of abelian varieties
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Mar 19 Tue Arthur Chatters (University of Bristol)
16:00 Generalised quaternions
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Mar 26 Tue John McCleary (Vassar (Cambridge))
16:00 Hochschild homology and closed geodesics
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Apr 2 Tue Kevin Houston (University of Leeds)
16:00 Images of Maps
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Apr 9 Tue Sarah Whitehouse (Sheffield)
16:00 Hopf algebras related to K-theory.
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Apr 17 Wed Mike Prest (Manchester)
16:00 Gabriel-Zariski spectra of module categories
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Apr 24 Wed Hugh Morton (Liverpool)
16:00 Algebras constructed from knot theory
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May 7 Tue Elizabeth Winstanley (Sheffield, Applied Mathematics)
16:00 1905 and all that: general relativity for algebraists
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May 8 Wed A.Veselov ( Loughborough)
16:00 Algebra and geometry of quantum Calogero-Moser problems
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May 14 Tue George Wilson (Imperial College)
16:00 Differential operators on algebraic varieties
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May 15 Wed L.O'Carroll ( Edinburgh)
16:00 Maximal Cohen-Macaulay modules over hypersurfaces: some algebra, some geometry, some history+D213
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May 21 Tue Simon Willerton (Sheffield)
16:00 Connections on gerbes
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May 22 Wed N.Yui (Queen's)
16:00 Mirror moonshine phenomena
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Sep 25 Wed Mr A Middleditch (Sheffield) Applied Mathematics Colloquium
Measuring ocean surface currents using HF radar
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Oct 2 Wed Prof Ronald Smith (Loughborough) Applied Mathematics Colloquium
The optimal compact finite-difference scheme for the diffusion equation with flow
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Oct 2 Wed T.Ward (UEA)
16:00 Commuting maps and commutative algebra
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Oct 9 Wed Dr Makis Kappos (Sheffield) Applied Mathematics Colloquium
Singularities, Far and Near
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Oct 9 Wed Ian Leary (Southampton)
16:00 An introduction to $L^2$ homology
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Oct 16 Wed Lars Hesselholt (MIT)
16:00 Algebraic K-theory and trace invariants
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Oct 23 Wed Dr I. Ballai (Sheffield) Applied Mathematics Colloquium
Coronal Seismology
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Oct 23 Wed Brooke Shipley (Purdue)
16:00 Rings up to homotopy
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Oct 30 Wed Dr D. Roscoe (Sheffield) Applied Mathematics Colloquium
Is dark matter the new phlogiston?
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Nov 6 Wed Dr Bill Lionheart (UMIST) Applied Mathematics Colloquium
Anisotropic inverse boundary value problems in electromagnetics
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Nov 13 Wed Rick Jardine (Western Ontario)
16:00 Presheaves of chain complexes
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Nov 20 Wed Dr V. Yudovich (Hull) Applied Mathematics Colloquium
Co-symmetry and its application in mechanics
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Nov 20 Wed A.Zalesski (UEA)
16:00 Hurwitz groups
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Nov 27 Wed Mr T. Antypas (Athens) Applied Mathematics Colloquium
The description of concentration time series of instantaneously released gases in the atmosphere via the proper orthogonal decomposition
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Nov 27 Wed Jan Schroer (Leeds)
16:00 On the Berenstein-Zelevinsky conjecture
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Dec 4 Wed Prof A. Hood (St. Andrews) Applied Mathematics Colloquium
Phase mixing: heating mechanism for coronal holes
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Dec 4 Wed Cho-Ho Chu (QMW)
16:00 Harmonic functions and random walks on groups
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Dec 11 Wed Prof Sir J. Kingman (Isaac Newton Institute) Applied Mathematics Colloquium
On teaching Poisson processes
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Dec 11 Wed P.Giblin (Liverpool)
16:00 Features of Surfaces
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Dec 18 Wed Frazer Jarvis (Sheffield)
16:00 The Fermat equation over real quadratic fields
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Jan 9 Thu Ieke Moerdijk (Utrecht)
16:00 Lie groupoids, gerbes and nonabelian cohomology
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Feb 5 Wed Dr Kristof Petrovay (Eotvos University, Budapest) Applied Mathematics Colloquium
Secondary shear instability in the solar tachocline
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Feb 12 Wed Dr Stephen Belcher (Reading, Meteorology) Applied Mathematics Colloquium
The role of surface waves in dynamics of the ocean mixed layer
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Feb 19 Wed Prof Ray Atkin (Sheffield) Applied Mathematics Colloquium
Inaugural lecture: Fluids with a future?
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Feb 21 Fri Dr Ingo Mueller-Wodarg (UCL, Atmospheric Physics Laboratory) Applied Mathematics Colloquium
The application of General Circulation Models to terrestrial and planetary upper atmospheres
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Feb 26 Wed Prof Vladimir Vladimirov (Hull) Applied Mathematics Colloquium
Virial equation in fluid dynamics
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Mar 5 Wed Dr Christos Vassilicos (Imperial College London, Aeronautics) Applied Mathematics Colloquium
Turbulent diffusion
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Mar 19 Wed Prof Alan Zinober (Sheffield) Applied Mathematics Colloquium
From the brachistochrone to the calculus of variations and modern control theory
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Mar 26 Wed Prof John Gibbon (Imperial College London) Applied Mathematics Colloquium
Infinite energy singularity formation in a class of solutions of the 3D Euler equations
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Apr 2 Wed Prof Farideh Honary (Lancaster) Applied Mathematics Colloquium
Modern Riometry: techniques and results
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May 6 Tue Prof Xia (China) Applied Mathematics Colloquium
Periodic orbits arising from delta-modulated feedback control
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May 7 Wed Prof Shadia Habbal (Aberystwyth, Physics) Applied Mathematics Colloquium
The solar wind and the hidden secrets of the Sun
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May 14 Wed Dr Eleri Pryse (Aberystwyth, Physics) Applied Mathematics Colloquium
Imaging near-Earth space
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May 29 Thu Dr Louise Harra (UCL, MSSL) Applied Mathematics Colloquium
Solar flare and Coronal Mass Ejections
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Oct 1 Wed Dr R. Balthazor (Sheffield) Applied Mathematics Colloquium
Modelling the Upper Atmosphere - a historical perspective
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Oct 1 Wed Charudatta Hajarnavis (University of Warwick)
16:00 A symmetry theorem for invertible ideals and its applications.
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Oct 8 Wed Dr N. Mole (Sheffield) Applied Mathematics Colloquium
Surface waves in random media: applications to solar physics
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Oct 22 Wed Dr Kristof Petrovay (Eotvos University, Budapest) Applied Mathematics Colloquium
The decay of sunspots as a nonlinear turbulent erosion process
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Oct 22 Wed Paul Turner (Heriot-Watt)
16:00 Putting the fields back into Topological Quantum Field Theory
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Oct 29 Wed Prof David Hughes (Leeds) Applied Mathematics Colloquium
Large- and small-scale dynamo action
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Oct 29 Wed Peter Rowlinson (Stirling)
16:00 Star complements in finite graphs
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Nov 5 Wed Dr Mervyn Freeman (British Antarctic Survey) Applied Mathematics Colloquium
Multi-scale Sun-Earth connections
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Nov 5 Wed Richard Thomas (Imperial)
16:00 Symmetry groups and geometrics PDEs
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Nov 12 Wed Dr John Brooke (CSAR, Manchester) Applied Mathematics Colloquium
Using Carrington's Legacy: analysing the spatio-temporal structure of the solar cycle from 1853 to 2003
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Nov 19 Wed Dr Alan Aylward (UCL, Physics and Astronomy) Applied Mathematics Colloquium
Solar variability and climate change: what CMAT model can tell us about the possible mechanisms
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Nov 19 Wed Tom Bridgeland (Edinburgh)
16:00 Moduli spaces and birational geometry
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Nov 26 Wed Dr William Wilkinson (CMIS, Brighton) Applied Mathematics Colloquium
The Earth's quasi-parallel bow shock: review of observations and outstanding questions
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Nov 26 Wed James McKee (Royal Holloway, University of London)
16:00 Salem numbers via interlacing
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Dec 10 Wed Prof Joe Buckley (Royal Military College of Canada, Physics) Applied Mathematics Colloquium
Ocean waves and microwaves
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Dec 10 Wed Peter Kropholler (Glasgow)
16:00 Classifying Spaces for Proper Group Actions
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Dec 17 Wed Dr Michael Warby (Brunel) Applied Mathematics Colloquium
The computational modelling of the constrained inflation of solid polymers in the context of thermoforming
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Dec 17 Wed Iain Gordon (Glasgow)
16:00 Symplectic reflection algebras.
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Feb 11 Wed Shahn Majid (Queen Mary, University of London)
16:00 Quantization of differential structures and quasiassociative geometry
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Feb 18 Wed Kohji Yanagawa (University of Osaka, Japan)
16:00 Stanley Reisner rings, Sheaves and Poincare-Verdier Duality
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Mar 3 Wed Roger Heath-Brown (Oxford)
16:00 Geometric problems in analytic number theory
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Mar 10 Wed Dr Itsuki Handoh (Sheffield) Applied Mathematics Colloquium
The mid-Cretaceous biogeochemical cycles and climate change
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Mar 10 Wed Colin Ingalls (Warwick)
16:00 Noncommutative Surfaces and Birational Geometry
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Mar 17 Wed Theodore Voronov (UMIST)
16:00 Higher derived brackets and homotopy algebras
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Mar 24 Wed Dr Elizabeth Lucek (ICSTM) Applied Mathematics Colloquium
Cluster observations of the Earth's bow shock
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Mar 24 Wed Shaun Bullett (Queen Mary, University of London)
16:00 Dynamics of Holomorphic Correspondences
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Mar 31 Wed Dr John Porrill (Sheffield, Psychology) Applied Mathematics Colloquium
Why neuroscience needs mathematicians?
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Mar 31 Wed Gavin Brown (University of Warwick)
16:00 Classification in algebraic geometry.
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Apr 28 Wed Dr David Tsiklauri (Salford, Computer Science and Engineering) Applied Mathematics Colloquium
Interaction of Alfven waves with plasma structures
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Apr 28 Wed Elizabeth Winstaley (University of Sheffield)
16:00 To Infinity and Beyond: Local and Global Geometry in General Relativity
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May 5 Wed Prof Slava Kurylev (Loughborough) Applied Mathematics Colloquium
Uniqueness and stability in multidimensional inverse problems
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May 5 Wed Kirill Mackenzie (University of Sheffield)
16:00 Duality for double and multiple structures
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May 12 Wed Dr David Roscoe (Sheffield) Applied Mathematics Colloquium
Discrete dynamical states in galactic discs: New insights, new data
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May 12 Wed Marcus du Satoy (Oxford)
16:00 Through the looking glass: groups from a number theoretic perspective
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May 17 Mon Vic Snaith (Southampton)
16:00 Stiefel-Whitney classes and symplectic local root numbers
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May 19 Wed Prof Viktor Shrira (Keele) Applied Mathematics Colloquium
Quasi-modes in shear flows: a working concept
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May 25 Tue Reinhold H (SAP)
16:00 Evolutions, derivations and differential forms
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May 26 Wed Tony Sudbery (University of York)
16:00 Quantum Information Theory: a confection of mathematics, physics and computer science
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May 28 Fri Linus Kramer (Darmstadt)
16:00 Buildings and Symmetric Spaces: Perspectives and Horizons
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Jun 29 Tue Stefan Bauer (Bielefeld)
16:00 Monopoles and Mergers in four Dimensions
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Sep 1 Wed Dr M. Miesch (HAO/NCAR, Boulder (USA)) Applied Mathematics Colloquium
Behind the HYPE: A Thin-Shell Model for the Solar Tachocline
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Sep 17 Fri Dr Hien Vo (Aberystwyth) Applied Mathematics Colloquium
Various aspects of the plasmasphere using satellite and ground data along with a study of the self-organizing criticality in using global auroral images
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Sep 29 Wed Dr E. Benilov (Limerick) Applied Mathematics Colloquium
Explosive instability in linear systems with stable eigenmodes
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Sep 29 Wed Neil Dummigan (Sheffield)
16:00 Elliptic Curves and Modular Degrees
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Sep 29 Wed Neil Dummigan (Sheffield) Pure Maths Colloquium
16:00 Elliptic Curves and Modular Degrees
Hicks Seminar Room J11
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Oct 6 Wed Dr R. Kerr (Warwick) Applied Mathematics Colloquium
Structure functions as a tool for atmospheric analysis
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Oct 6 Wed Ben Green (Cambridge) Pure Maths Colloquium
16:00 Arithmetic progressions of primes
Hicks Seminar Room J11
  Abstract:
I will discuss some aspects of the recent proof that there are arbitrarily long arithmetic progressions of primes, which is joint work with Terry Tao. I will also discuss some more recent work of ours, which gives an asymptotic for the number of 4-term APs of primes, all less than N.
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Oct 13 Wed Dr W. Chaplin (Birmingham, Physics and Astronomy) Applied Mathematics Colloquium
Sounding the deep solar interior: modern challenges for global Helioseismology
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Oct 14 Thu Bernhard Hanke (Munich) Pure Maths Colloquium
14:00 Enlargeability and index theory
Hicks Seminar Room J11
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Oct 20 Wed Dr A. Ferriz-Mas (Vigo, Spain) Applied Mathematics Colloquium
Fluid mechanical aspects in solar magnetism: How can magnetic fields of 100 kG be produced?
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Oct 20 Wed Burt Totaro (Cambridge) Pure Maths Colloquium
16:00 Topological Invariants of Singular Varieties
Hicks Seminar Room J11
  Abstract:
We start with some examples of singularities that algebraic varieties can have in low dimensions. We look at resolutions of singularities, that is, mappings from a smooth manifold onto a singular space. One can try to define invariants of a singular space using known invariants of its resolution. I will describe some successful invariants of this type: intersection homology theory, the elliptic genus, and stringy Betti numbers.
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Oct 27 Wed Prof I. Moss (Newcastle) Applied Mathematics Colloquium
Warm inflation and the hot big bang
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Oct 27 Wed Jan Schroer (Leeds) Pure Maths Colloquium
16:00 Universal Bases for Kac-Moody Lie Algebras
Hicks Seminar Room J11
  Abstract:
The talk aims to explain the connection between the following topics: - Canonical Bases for Kac-Moody Lie Algebras - Representation Theory of Preprojective Algebras - Varieties of Modules.
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Nov 3 Wed Prof G. Tallents (York, Physics) Applied Mathematics Colloquium
The opacity of hot dense plasmas: application to laboratory and solar examples
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Nov 3 Wed Roger Plymen (Manchester) Pure Maths Colloquium
16:00 Two-by-two matrices from two points of view
Hicks Seminar Room J11
  Abstract:
This will mainly be about SL(2,C) and SL(2,R). The first point of view is that of Harish-Chandra, and leads to irreducible unitary representations, the Plancherel measure and the tempered dual. The second point of view is that of Connes and Kasparov, which leads from the reduced C*-algebra back to the representations rings R(SU(2)) and R(SO(2)). I will relate these two points of view, and describe recent results for GL(3) (joint work with Anne-Marie Aubert).
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Nov 10 Wed David Calderbank (Edinburgh) Pure Maths Colloquium
16:00 Toric selfdual Einstein metrics
Hicks Seminar Room J11
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Nov 11 Thu Prof S. Quegan (Sheffield) Applied Mathematics Colloquium
A short walk around the Carbon cycle
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Nov 17 Wed Peter Larcombe (Derby) Pure Maths Colloquium
16:00 Some Recent Results on Catalan Numbers and Catalan-Related Sequences
Hicks Seminar Room J11
  Abstract:
In this talk I will give a brief introduction to the well known Catalan number and present research results associated with them, some of which are set in historical context. Two recently announced Catalan-related sequences which arise from elliptic integrals---namely, the so called Catalan-Larcombe-French and Fennessey-Larcombe-French---are then introduced, and their properties discussed.
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Nov 18 Thu Dr N. Mavromatos (King's College, London) Applied Mathematics Colloquium
CPT violation and decoherence: is there a chance of observing something?
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Nov 24 Wed Dr P. Browning (UMIST) Applied Mathematics Colloquium
Heating the solar corona by nanoflares
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Nov 24 Wed Michael Farber (Durham) Pure Maths Colloquium
16:00 Topology of Robot Motion Planning
Lecture Theatre 2, Hicks Building
  Abstract:
In the talk I will show that one may predict the character of instabilities of robot's behavior knowing the cohomology algebra of its configuration space.
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Nov 26 Fri Prof P. Diamond (UCSD) Applied Mathematics Colloquium
Zonal flows in Laboratory plasmas
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Dec 1 Wed Imre Leader (Cambridge) Pure Maths Colloquium
16:00 Partition Regular Equations
Hicks Seminar Room J11
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Dec 7 Tue Alfonso Gracia--Saz (UC Berkeley)
Duality of triple structures and beyond
  Abstract:
A double vector bundle is a commutative diagram $$\xymatrix{ D \ar[r] \ar[d] & B \ar[d] \\ A \ar[r] & M }$$ where every vertex is a smooth manifold, every edge is a vector bundle, plus compatibility conditions between the two structures on $D$. $D$ can be dualized with respect to these 2 structures. These 2 dualization operations have order 2, but do not commute, and generate a group isomorphic to the symmetric group $S_3$. Mackenzie found a geometric interpretation and started the study of triple vector bundles, which is not a straightforward generalization. We will show recent work on the calculation of the group generated by the $n$ dualizations of a $n$--fold vector bundle, which turns out to be a central extension of $S_{n+1}$ by ${n\choose 2} - 1$ copies of $C_2$.
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Dec 8 Wed Dr E. Winstanley (Sheffield) Applied Mathematics Colloquium
What Hawking did: why all the fuss in Dublin?
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Dec 8 Wed Dave Applebaum (Sheffield) Pure Maths Colloquium
16:00 Harmonic Analysis of Semigroups of Measures on Locally Compact Groups
Hicks Seminar Room J11
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Dec 15 Wed Dr C. van de Bruck (Sheffield) Applied Mathematics Colloquium
Cosmology and Extra Dimensions
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Dec 15 Wed Victor Flynn (Liverpool) Pure Maths Colloquium
16:00 Visualisation in Higher Genus
Hicks Seminar Room J11
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Jan 13 Thu Larry Smith (G)
16:00 Macaulay Duals for Hilbert Ideals of Reflection Groups
Hicks Seminar Room J11
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Feb 1 Tue Samuel W (Sheffield) Topology Seminar
16:00 I-adic towers and Koszul complexes in algebra and topology
Hicks Seminar Room J11
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Feb 8 Tue Samuel W (Sheffield) Topology Seminar
14:00 I-adic towers and Koszul complexes in algebra and topology
Hicks Seminar Room J11
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Feb 9 Wed Dr J. J. Healey (Keele) Applied Mathematics Colloquium
A strange instability with growth normal to a boundary layer
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Feb 9 Wed Victor Snaith (Sheffield) Pure Maths Postgraduate Seminar
12:00 Algebraic topology at work: the non-existence of maps of Hopf invariant one
Hicks Seminar Room J11
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Feb 9 Wed Peter Cameron (Queen Mary) Pure Maths Colloquium
16:00 The Rado graph and the Urysohn space
Hicks Seminar Room J11
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Feb 14 Mon Moty Katzman (Sheffield) Algebra / Algebraic Geometry seminar
16:10 Graphs and their ideals
Hicks Seminar Room J11
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Feb 15 Tue Samuel W (Sheffield) Topology Seminar
14:00 I-adic towers and Koszul complexes in algebra and topology
Hicks Seminar Room J11
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Feb 16 Wed Dr D. Roscoe (Sheffield) Applied Mathematics Colloquium
Reaction in classical electrodynamics
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Feb 16 Wed Sam Marsh (Sheffield) Pure Maths Postgraduate Seminar
12:10 $F_{l}$-representations of finite abelian $p$-groups
Hicks Seminar Room J11
  Abstract:
to appear
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Feb 16 Wed Rob de Jeu (Durham) Pure Maths Colloquium
16:00 Algebraic K-theory of number fields, regulators, zeta- functions,....
Hicks Seminar Room J11
  Abstract:
We discuss relations between the K-theory of number fields and their zeta functions, both classically and (more conjecturally) p- adically. Apart from talking about the theoretical description of those regulators we also touch upon aspects on how to compute them in practice.
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Feb 21 Mon Victor Snaith (Sheffield) Algebra / Algebraic Geometry seminar
16:10 Stickelberger series Part IV
Hicks Seminar Room J11
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Feb 22 Tue Samuel W (Sheffield) Topology Seminar
14:00 I-adic towers and Koszul complexes in algebra and topology
Hicks Seminar Room J11
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Feb 23 Wed Dave Barnes (Sheffield) Pure Maths Postgraduate Seminar
12:10 Rational homotopy of spheres
Hicks Seminar Room J11
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Feb 28 Mon Victor Snaith (Sheffield) Algebra / Algebraic Geometry seminar
16:10 Stickelberger V
Hicks Seminar Room J11
  Abstract:
This is the last in the Stickelberger series. In this one, finally the BIG CONJECTURE will be revealed and a sketch proof of the evidence for it will be given.
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Mar 1 Tue Neil Strickland (Sheffield) Topology Seminar
14:00 Morava K-theory I
Hicks Seminar Room J11
  Abstract:
I will give a series of three or four lectures introducing Morava K-theory and Morava E-theory.
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Mar 2 Wed Dr J. Kaplunov (Manchester) Applied Mathematics Colloquium
Explicit asymptotic models for surface elastic and electroelastic waves
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Mar 2 Wed Nong Sasom (Sheffield) Pure Maths Postgraduate Seminar
12:10 Leonard triples and the quintization of U(sl2)
Hicks Seminar Room J11
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Mar 2 Wed Andrei Lazarev (Bristol) Pure Maths Colloquium
16:00 p-divisible groups associated to generalized cohomology theories of Eilenberg-Mac Lane spaces
Hicks Seminar Room J11
  Abstract:
It is well-known that a generalized cohomology theory applied to the infinite dimensional complex projective space $CP^\infty$ often gives rise to a one-dimensional group law. This fact has innumerable applications in stable homotopy theory. One particularly important class of a one dimensional formal group is associated with $K(n)^* CP^\infty)$ where $K(n)$ is the nth Morava K-theory. This is an essentially unique example of a one-dimensional formal group of height $n$ over a field. It turns out that if one replaces $CP^n=K(Z,2)$ with $K(Z,l) $, the integral Eilenberg-Mac Lane space with $\pi_l=Z$ then the corresponding object is a formal group of finite height (a.k.a. smooth p-divisible group). This is essentially a 25 year old result of Ravenel-Wilson although they did not phrase it in this way. Letting l vary we obtain a collection of p-divisible groups which possesses a remarkable symmetry. Particularly, any p- divisible group enters in this collection together with its Serre dual (an analogue of the notion of principal polarization for abelian schemes). This and related results are obtained by studying the Dieudonne modules associated to the corresponding p- divisible groups. This is a joint work of myself with Victor Buchstaber.
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Mar 7 Mon Holger Brenner (Sheffield) Algebra / Algebraic Geometry seminar
16:10 The Frobenius homomorphism - what it annihilates and how fast
Hicks Seminar Room J11
  Abstract:
Let C denote a smooth projective curve over a field of positive characteristic p. We consider a cohomology class $c \in H^1 (C,S)$ for a vector bundle S over C and ask whether c is annihilated by some power of the absolute Frobenius on C -- and if so, which power annihilates it. This question is related to the computation of the Frobenius closure of an ideal in the coordinate ring over C.
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Mar 9 Wed Dr C. Mandrini (IAFE, Argentina) Applied Mathematics Colloquium
Magnetic Helicity: linking solar to interplanetary phenomena
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Mar 9 Wed Mike Holcombe (Sheffield, Computer Science) Pure Maths Colloquium
16:00 Algebraic techniques for Software Testing
Hicks Seminar Room J11
  Abstract:
Software testing is the most expensive and difficult part of the software production process. IBM, for example estimate that testing and reviewing activities account for at least 50% of any project, in safety critical projects it can reach 90%. The sales of software in the UK in 2001 was
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Mar 14 Mon Manuel Blickle (Essen) Algebra / Algebraic Geometry seminar
16:10 Local cohomology multiplicities via etale cohomology
Hicks Seminar Room J11
  Abstract:
I will show how certain local cohomology invariants (introduced by Lyubeznik) can be completely described in terms of etale cohomology. This generalizes earlier known results, which gave a topological description of these invariants for isolated complex singularities, in two different directions. For once our techniques apply to a significantly larger class of singularities (in particular all complete intersections are inluded) and secondly (and more importantly) our results are valid in positive characteristic also. I will use this result as an excuse to explain a recent Riemann--Hilbert--type correspondence due to Emerton-- Kisin which is the tool that allows us to also treat the positive characteristic case.
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Mar 15 Tue Neil Strickland (Sheffield) Topology Seminar
14:00 Morava K-theory III
Hicks Seminar Room J11
  Abstract:
I will discuss the Morava K-theory of various spaces, such as classifying spaces of finite groups.
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Mar 16 Wed Mary-Jane Strong (Sheffield) Pure Maths Postgraduate Seminar
12:10 An introduction to Hopf algebras
Hicks Seminar Room J11
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Mar 16 Wed Nick Shepherd-Barron (Cambridge) Pure Maths Colloquium
16:00 Geometry of tangent bundles and effective Mordell over function fields.
Hicks Seminar Room J11
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Apr 12 Tue Al Weiss (University of Alberta)
14:00 tba
Hicks Seminar Room J11
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Apr 13 Wed Dr J. Winkler (Sheffield, Computer Science) Applied Mathematics Colloquium
A comparison of condition numbers of the full rank least squares problem
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Apr 13 Wed Ian Young (Sheffield) Pure Maths Postgraduate Seminar
12:10 Alice, Bob and elliptic curves
Hicks Seminar Room J11
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Apr 13 Wed Bernhard Koeck (Southampton) Pure Maths Colloquium
16:00 The Chevalley-Weil formula in positive characteristic.
Hicks Seminar Room J11
  Abstract:
Let G be a finite group acting on an algebraic curve X. This action induces an action on various Riemann-Roch spaces such as the vector space of global holomorphic differentials on X. We determine these (modular) representations in local terms, thereby generalizing the classical Chevalley-Weil formula from characteristic 0 to the so-called weakly ramified case, an important case of wild ramification.
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Apr 18 Mon Andrew Stacey (Sheffield) Topology Seminar
14:00 The Differential Topology of Loop Spaces I
Hicks Seminar Room J11
  Abstract:
The aim of these seminars is to provide a gentle but detailed introduction to the study of loop spaces as manifolds. This is a topic which has a long history, dating back at least to the days of Morse, and which has recently received renewed interest due to its strong links with string theory. We shall end this mini-series with an overview of my work on the Dirac operator on loop spaces. This finale will dictate the itinery of the tour: 1. What is an infinite dimensional manifold and how do we know that the loop space is one? 2. What does it look like, what can we do with it, and what do we want to do with it? 3. What's the big deal about Dirac operators in infinite dimensions? It is intended that anyone with basic differential topology should be able to follow these seminars.
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Apr 20 Wed Dr Gunnar Hornig (St. Andrews) Applied Mathematics Colloquium
Three-dimesional magnetic reconnection
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Apr 20 Wed Phil Martin (Sheffield) Pure Maths Postgraduate Seminar
12:10 tba
Hicks Seminar Room J11
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Apr 20 Wed Ivan Tomasic (Lyon) Pure Maths Colloquium
16:00 Weil conjectures--with a difference
Hicks Seminar Room J11
  Abstract:
While the classical Weil conjectures are concerned with counting points on varieties over finite fields, we consider the problem of counting points on \emph {difference} varieties over algebraic closures of finite fields with powers of Frobenius. This context is suitable e.g. for uniform treatment of Ree and Suzuki families of finite simple groups.
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Apr 26 Tue Andrew Stacey (Sheffield) Topology Seminar
15:00 The Differential Topology of Loop Spaces II
Hicks Seminar Room J11
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Apr 27 Wed Prof. Carlo Barenghi (Newcastle) Applied Mathematics Colloquium
The Taylor-Couette problem: an old flow with new twists
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Apr 27 Wed Vicky Hinchcliffe (Sheffield) Pure Maths Postgraduate Seminar
12:10 Gelfand-Kirillov dimension
Hicks Seminar Room J11
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Apr 27 Wed Nick Bingham (Sheffield, Probability and Statistics) Pure Maths Colloquium
16:00 Mercerian theorems
Hicks Seminar Room J11
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May 3 Tue Andrew Stacey (Sheffield) Topology Seminar
15:00 The Differential Topology of Loop Spaces III
Hicks Seminar Room J11
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May 4 Wed Dr Erwin Verwichte (Warwick) Applied Mathematics Colloquium
Transverse waves in the solar corona
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May 4 Wed Alan Lauder (Oxford) Pure Maths Colloquium
16:00 Title: Effective methods in rigid cohomology
Hicks Seminar Room J11
  Abstract:
Given a system of polynomial equations over a finite field, one may associate with it a finite dimensional vector space, known as the ``rigid cohomology'' of the system. This construction is very useful; for example, it allows one to prove good bounds on the number of solutions to the system over the finite field (Weil conjectures). The construction was first proposed in the 1960s; however, showing that the vector spaces it associated with systems were finite dimensional turned out to be very difficult. (This was not done until the mid 1990s, independently by Berthelot and Christol-Mebkhout.) In my talk I will discuss an ``effectivity problem'' related to the finiteness of the rigid cohomology of a system of equations.
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May 10 Tue Dr Anthony Field (Culham Laboratory) Applied Mathematics Colloquium
How to make 100 million a day, 100 million degrees C - the temperature at which plasma burns
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May 10 Tue Sarah Whitehouse (Sheffield) Topology Seminar
15:10 Stable and unstable K-theory operations
Hicks Seminar Room J11
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May 11 Wed Joe Chuang (Bristol) Pure Maths Colloquium
16:00 Representation theory with rhombus tilings
Hicks Seminar Room J11
  Abstract:
I'll discuss some joint work with Will Turner on certain algebras associated to tilings of the plane by rhombi. These `rhombal algebras' defined by Michael Peach were inspired by the representation theory of symmetric groups in positive characteristic. There is a close connection between the combinatorics of the tilings and the homological properties of the algebras. For example certain basic mutations of tilings correspond to equivalences of derived categories of modules.
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May 17 Tue Mike Mandell (Cambridge) Topology Seminar
15:10 A Localization Sequence for the Algebraic K-Theory of Topological K-Theory
Hicks Seminar Room J11
  Abstract:
In many ways the algebraic K-theory of ring spectra behaves like the algebraic K-theory of traditional rings. One limitation is the lack of a general formulation of a devissage theorem. Recent work (joint with Andrew Blumberg) establishes one very special case of the devissage theorem. This case is sufficient to construct the localization sequence conjectured by Rognes relating the algebraic K-theory of (complex) K-theory, connective K- theory, and the integers.
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May 18 Wed Dr Sergey Nazarenko (Warwick) Applied Mathematics Colloquium
Turbulence of sea waves
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May 19 Thu David Elworthy (Warwick)
14:00 Stochastic Flows and Universal Connections
K14
  Abstract:
There are various places where the geometrical notion of a connection appears in stochastic analysis. In this expository talk I shall describe some of these, and show how they are related; first describing what they are and are useful for: in fact the more general notion of a non- linear semi- connection will be needed. For probabilists I'll indicate how they might (perhaps...) be useful for such problems as - trying to estimate the behaviour of an oil slick (on the surface of a curved planet, acted on by random forces) given the behaviour of one of its particles. For geometers/ topologists the constructions involved relate to the classifying spaces for gauge groups of subbundles of tangent bundles. This talk is mainly taken from joint work with Yves LeJan and Xue-Mei Li, see http://xuemei.org/bib.html.
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May 24 Tue Ieke Moerdijk (Sheffield) Topology Seminar
15:00 What do classifying spaces classify?
Hicks Seminar Room J11
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May 25 Wed Dr Nils Andersson (Southampton) Applied Mathematics Colloquium
Gravitational-wave asteroseismology - probing the extremes of physics
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May 25 Wed Luis Hernandez-Hernandez (Sheffield) Pure Maths Postgraduate Seminar
12:10 Fixed point degrees of equivariant maps of spheres
Hicks Seminar Room J11
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May 25 Wed Srikanth Iyengar (Nebraska) Pure Maths Colloquium
16:00 Levels in triangulated categories and perfect complexes over commutative rings
Hicks Seminar Room J11
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May 31 Tue Neil Strickland (Sheffield) Topology Seminar
15:10 The Rezk logarithm I
Hicks Seminar Room J11
  Abstract:
The Rezk logarithm is a natural map $(E^0X)^\times\rightarrow E^0X$ defined for all spaces $X$ and suitable generalised cohomology theories $E$. In many cases it is close to being an isomorphism. There is a simple definition using a functor constructed by Bousfield and Kuhn, but the thing that makes it usable is a theorem of Rezk relating it to the theory of power operations, and in particular the Hecke operators studied by Ando. This seminar will be the first of a series covering some of this material.
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Jun 7 Tue Neil Strickland (Sheffield) Topology Seminar
15:10 The Rezk logarithm II
Hicks Seminar Room J11
  Abstract:
I will talk about generalized Moore spectra, K(n)-localisation, and the Bousfield-Kuhn functor, all of which are ingredients in the definition of the Rezk logarithm.
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Jun 17 Fri Hellen Colman (Wilbur Wright College, Chicago, USA) Pure Maths Colloquium
16:00 Lusternik-Schnirelmann category for orbifolds
Hicks Seminar Room J11
  Abstract:
We define and study a Lusternik-Schnirelmann theory for orbifolds. The orbifold category provides a new invariant of the homotopy type of the orbifold that gives a numerical measure of the complexity of the orbifold $X$. In particular, the orbifold category gives a lower bound on the number of critical points of any orbifold smooth function $f\colon X\rightarrow R$. We use equivariant methods to find upper and lower bounds on the orbifold category in terms of the orbifold resolution of the singular set. We obtain a generalization of the classical cohomological lower bound for orbifold category using the orbifold cohomology theory constructed by Chen-Ruan.
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Jul 5 Tue Neil Strickland (Sheffield) Topology Seminar
15:10 The Rezk Logarithm II'
Hicks Seminar Room J11
  Abstract:
I will talk about generalized Moore spectra, K(n)-localisation, and the Bousfield-Kuhn functor, all of which are ingredients in the definition of the Rezk logarithm. This will essentially be a repeat of the seminar I gave a few weeks ago when many people were away.
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Sep 20 Tue Yoshi Maeda (Keio University, Japan) Pure Maths Colloquium
16:00 Deformation quantizations and gerbes
Lecture Theatre 6
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Sep 28 Wed Dr Stephen Davies (Leiden) Applied Mathematics Colloquium
Constraining Gauss-Bonnet Dark Energy
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Sep 28 Wed Peter Symonds (Manchester) Pure Maths Colloquium
16:10 Group actions on polynomial rings
Hicks Seminar Room J11
  Abstract:
We consider a polynomial ring $k[x_1,...,x_n]$ over a finite field $k$ and suppose that some finite group $G$ acts on it by linear substitutions. We want to understand the ring as a $kG$-module. We present a structure theorem that describes this in a finite way. It has several notable corollaries, such as the fact that only finitely many indecomposable modules occur as summands (up to isomorphism) and the fact that we can write down an a priori bound on the degrees of the generators of the invariant subring.
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Oct 3 Mon Tom Bridgeland (Sheffield)
14:00 Mirror symmetry I
Hicks Seminar Room J11
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Oct 4 Tue Johann Sigurdsson (Sheffield) Topology Seminar
14:00 Duality in parametrized homotopy theory
Hicks Seminar Room J11
  Abstract:
I will describe formal structure enjoyed by the parametrized stable homotopy categories and how one can encode it into a single bicategory. I will then discuss duality theory from that perspective and show how it gives simple conceptual proofs of generalizations of various known duality phenomena such as Atiyah duality and the Wirthmuller and Adams equivalences. The talk should be accessible to everyone.
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Oct 5 Wed Dr Steven Tobias (Leeds) Applied Mathematics Colloquium
The role of spectra in dynamo theory - does mean-field modelling make any sense?
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Oct 5 Wed Graham Everest (East Anglia) Pure Maths Colloquium
16:00 Bilinear Recurrence Sequences
Hicks Seminar Room J11
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Oct 7 Fri Yukinobu Toda (Tokyo)
14:00 Deformations and Fourier-Mukai transform
Hicks Seminar Room J11
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Oct 10 Mon Tom Bridgeland (Sheffield)
14:00 Mirror symmetry II
Hicks Seminar Room J11
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Oct 11 Tue Johann Sigurdsson (Sheffield) Topology Seminar
14:00 Duality in parametrized homotopy theory
Hicks Seminar Room J11
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Oct 12 Wed Rapha (Leeds) Pure Maths Colloquium
16:00 Dunkl operators and Hecke algebras
Hicks Seminar Room J11
  Abstract:
The first parts of my talk will be very elementary. I will introduce a deformation of the ordinary derivation of real functions of one variable. I will discuss the corresponding operator on polynomials (for which values of the deformation parameter are there non constant polynomials killed by the operator ?) and on analytic functions (spectrum of the operator, eigenfunctions as Bessel functions). Then, I will switch to the dimension $n$ case, where one has a commuting family of operators deforming the $d/dx_i$ (the Dunkl operators). I will focus on the action on polynomial functions of $n$ variables and explain how this is controlled by an algebra deforming the algebra of polynomial differential operators (a doubly degenerate double affine Hecke algbra). This leads to the study of representations of this algebra. I will describe how the representation theory of this algebra is studied, in analogy with the representation theory of the Lie algebra $gl_n(\mathbb{C})$. This last part brings a lot of exciting mathematics:
  • Knizhnik-Zamolodchikov equations, braid groups, Hecke algebras to analyze representations as systems of differential equations.
  • quantum general linear group, Fock spaces to describe precisely the representation theory
  • Hilbert scheme of points on $\mathbb{C}^2$ as the geometric object connected to the representation theory.
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Oct 13 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Overview of the Beilinson conjectures.
Hicks Seminar Room J11
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Oct 14 Fri Victor Snaith (Sheffield) Pure Maths Postgraduate Seminar
11:10 Monomial Representations
Hicks Seminar Room J11
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Oct 14 Fri Moty Katzman (Sheffield)
14:00 Ideals of minors of matrices with indeterminate entries
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Oct 17 Mon Tom Bridgeland (Sheffield)
14:00 Mirror symmetry III
Hicks Seminar Room J11
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Oct 18 Tue Simon Willerton (Sheffield) Topology Seminar
14:00 The derived category of sheaves on a complex manifold from a representation theory perspective
Hicks Seminar Room J11
  Abstract:
I will try to explain how the derived category of sheaves on a complex manifold (which I will remind you of) looks a lot like the representation category of a finite group. This will be motivated by ideas from topological field theory.
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Oct 19 Wed Karima Khusnutdinova (Loughborough) Applied Mathematics Colloquium
The effect of bubbles on internal waves
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Oct 19 Wed Alexander Stasinski (University of East Anglia) Pure Maths Colloquium
16:00 Representations of reductive groups over finite rings
Hicks Seminar Room J11
  Abstract:
Let $F$ be a local field with finite residue field, ring of integers $O$, and maximal ideal $p$. Let $G$ be a reductive group scheme over $O$ (e.g. $G=GL_n$). We present an approach to the study of representations of the finite groups $G_{r}:=G(O/p^r)$, which for $r=1$ coincides with the theory of Deligne and Lusztig. One reason why such a study is of interest is the close connection between the representation theory of the groups $G_{r}$, and the representation theory of the group $G(F)$. One of the few cases where the representations of $G_{r}$ are known for all $r;eq1$, is when $G=GL_{2}$. This is due to several people, including Kutzko, and the method used is purely algebraic, and quite different from our geometric approach. We show how the two methods can be linked, and in particular how the algebraic method can be used to analyse representations constructed geometrically.
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Oct 20 Thu Victor Snaith (Sheffield)
12:10 Overview of the Beilinson Conjectures II
Hicks Seminar Room J11
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Oct 25 Tue David Gepner (Sheffield) Topology Seminar
14:00 Equivariant elliptic cohomology
Hicks Seminar Room J11
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Oct 26 Wed Reza Raoufi and Alan Zinober (Sheffield) Applied Mathematics Colloquium
$C^3$ = Chaos, Cryptography and Control
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Oct 26 Wed Dietrich Notbohm (University of Leicester) Pure Maths Colloquium
16:00 Homology decompositions and applications
Hicks Seminar Room J11
  Abstract:
A homolgy decomposition is a way to build a space out of 'simpler' space. A CW -complexes is given an iterated building process based on spheres and discs where as the gluing data for homology decompositions is encoded in a functor defined on a 'nice' category with values in the category of topological spaces, and where all simpler spaces are glued together in one step. Homology decompositions are one of the major tools to understand the homotopy theory of classifying spaces. We will apply these ideas in several much more algebraic contexts, Stanley-Reisner algebras associated to simplicial complexes, invariant theory and group cohomology.
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Oct 27 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Overview of the Beilinson conjectures III.
Hicks Seminar Room J11
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Oct 28 Fri Paul Buckingham (Sheffield) Pure Maths Postgraduate Seminar
11:10 Sheaf Cohomology and hypercohomology
Hicks Seminar Room J11
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Oct 28 Fri Almar Kaid (Sheffield) Algebra / Algebraic Geometry seminar
14:00 Unitarily graded field extensions
Hicks Seminar Room J11
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Nov 2 Wed Prof. Howard Wilson (York) Applied Mathematics Colloquium
Explosive instabilities in laboratory fusion plasmas
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Nov 2 Wed Marcus Linckelmann (Aberdeen) Pure Maths Colloquium
16:00 Fusion Systems and Modular Representation Theory
Hicks Seminar Room J11
  Abstract:
The $p$-local approach to finite group theory tries to understand the structure of a finite group in terms of one of its Sylow-$p$-subgroups $P$ (they are all isomorphic, so it doesn't matter which one we take) and the way in which $P$ is embedded into $G$. This approach goes well back to the early stages of the theory, illustrated by theorems of Burnside and Frobenius, and plays an important role in the context of the classification of finite simple groups. One can describe the p-local structure of $G$ in terms of a category, the fusion system of $G$. As a consequence of work of Alperin and Broue around 1980 it appears that categories with very similar formal properties occur also in modular representation theory, prompting Puig in the 1990's to formalise the notion of fusion systems independently of finite groups and Benson to speculate whether any such fusion system gives rise to a topological space which would play the role of classifying space of the group. Broto, Levi and Oliver developed in recent years the precise framework for topological spaces arising in this way - giving a sense to the concept of classifying spaces of finite groups which don't exist...
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Nov 3 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Overview of Beilinson's conjectures IV
Hicks Seminar Room J11
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Nov 4 Fri Sam Marsh (Sheffield) Pure Maths Postgraduate Seminar
11:10 TBA
Hicks Seminar Room J11
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Nov 4 Fri David Jordan (Sheffield) Algebra / Algebraic Geometry seminar
14:00 Poisson algebras and modules: a case study.
Hicks Seminar Room J11
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Nov 9 Wed Everett Howe (Center for Communications Research, San Diego) Pure Maths Colloquium
16:00
Hicks Seminar Room J11
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Nov 10 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Overview of Beilinson's conjectures V
Hicks Seminar Room J11
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Nov 11 Fri Victor Snaith (Sheffield) Snaith seminar
10:00 The Arf Invariant One Problem Part I
Hicks Seminar Room J11
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Nov 11 Fri David Barnes (Sheffield) Pure Maths Postgraduate Seminar
11:10 Theory of Representations and Stable Homotopy
Hicks Seminar Room J11
  Abstract:
The speaker has been overheard referring to this subject (acronymoniously)as T.R.A.S.H.
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Nov 11 Fri Victor Snaith (Sheffield) Snaith seminar
14:00 The Arf Invariant One Problem Part II
Hicks Seminar Room J11
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Nov 14 Mon Prof. Stanley L Jaki (Seton Hall) Applied Mathematics Colloquium
A late awakening with a nightmare
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Nov 14 Mon Stanley L. Jaki (Seton Hall University) Pure Maths Colloquium
16:00 A late awakening with a nightmare
LT5
  Abstract:
According to Godel's theorem, formulated in 1930, no non- trivial theory of arithmetic can have its proof of consistency in terms of the presuppositions of the theory itself. This means that it is not possible to form a final form of mathematics that would be its sole form which is also necessarily true. Since physics has to be heavily mathematical, this also means the end of hopes that a final physical theory could ever be formulated. Contrary to a recent claim of Prof Hawking, this does not mean of the end of physics, though it constitutes a death blow at those hopes, often proposed with great arrogance. Godel's theorem is an assurance that the work of physicists will go on to no end.
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Nov 15 Tue Andrew Stacey (Sheffield) Topology Seminar
14:00 Delooping Moravian Maps
Hicks Seminar Room J11
  Abstract:
One of the pieces of baggage that comes with a graded cohomology theory is the family of operations. These are self-maps of the cohomology groups obeying certain obvious naturality conditions. There are two main types of operation: stable and unstable. An unstable operation acts only on the cohomology groups of a particular degree whilst a stable operation acts on the cohomology groups of any degree compatibly with the suspension isomorphism. It is clear, therefore, that a stable operation defines a family of unstable ones. However, even if one knows that an unstable operation came from a stable one it may not be easy to reconstruct that stable operation. What is remarkable about the Morava K--theories is that there is a straightforward way to do this. The "delooping" of the title refers to the fact that operations are closely linked to maps between certain spaces and spectra associated to the cohomology theory. In this language, the claim is that there is a simple way to convert an arbitrary map between the representing spaces of the Morava K-theories into an infinite loop map. The mathematics involved is astonishingly simple and I shall endeavour to keep the exposition in a similar vein. Thus the prerequisites are minimal: a familiarity with cohomology theories and their links with spectra. This work is joint with Sarah Whitehouse and is funded as part of the EPSRC project on operations in Morava K--theories.
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Nov 16 Wed Dr A Thyagaraja (Culham Laboratory) Applied Mathematics Colloquium
Mesoscale electromagnetic turbulence in tokamaks
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Nov 16 Wed Mark Watkins (Bristol) Pure Maths Colloquium
16:00 Special values of L-functions: a meeting place of algebra and analysis.
Hicks Seminar Room J11
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Nov 18 Fri Ian Young (Sheffield) Pure Maths Postgraduate Seminar
11:10 L-functions and elliptic curves
Hicks Seminar Room J11
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Nov 18 Fri David Jordan (Sheffield) Algebra / Algebraic Geometry seminar
14:00 Poisson algebras and modules: a case study II
Hicks Seminar Room J11
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Nov 22 Tue Ruben Sanchez (Sheffield) Topology Seminar
14:00 Classifying spaces for proper actions and the Baum-Connes Conjecture
Hicks Seminar Room J11
  Abstract:
I will explain how to generalize the ordinary classifying space of a group G to actions with finite stabilizers. The corresponding classifying space appears in the Baum-Connes Conjecture, which identifies two objects associated to G, one analytical and one topological. The analytical one is the K-theory of the reduced $C^*$-algebra of G, and the topological one is the equivariant K-homology of this classifying space. I will describe how to use Bredon homology and a spectral sequence to obtain the topological side of Baum-Connes. Then I would like to explain how to do this for the groups $SL(3,\mathbb{Z})$ and for some Coxeter groups. The talk may suit two sessions, so if people are not too unhappy, I may also talk the following week.
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Nov 23 Wed Prof. Yurii Sergeev (Newcastle) Applied Mathematics Colloquium
Tracer particles in turbulent helium II at low temperatures
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Nov 23 Wed Paul Buckingham (Sheffield)
01:30 Serre's Modularity Conjecture "Recipe for the weight"
Hicks Seminar Room J11
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Nov 23 Wed Aaron Lauda (Cambridge) Pure Maths Colloquium
16:00 Frobenius algebras and thick tangles
Hicks Seminar Room J11
  Abstract:
In topological quantum field theory one is interested in studying functors from a topological category of $n$-dimensional cobordisms into the category of vector spaces. In two dimensions such functors are very well understood. In fact, specifying a (symmetric monoidal) functor from the 2-dimensional cobordism category 2-Cob into Vect is equivalent to specifying a commutative Frobenius algebra. This makes the study of 2-dimensional TQFT's particularly simple. Recent developments in string theory have prompted many to consider topological quantum field theories using a more interesting version of the $2$-dimensional cobordism category, namely one that allows for cobordisms between $1$-manifolds with boundary. In this talk I will define a category of planar cobordisms between `open strings' and show that functors from this category into Vect are equivalent to (not necessarily commutative) Frobenius algebras. This result arises naturally by considering adjunctions in 2- categories. If time permits, I will also sketch how this process can be generalized to higher-dimensional surfaces using higher-dimensional category theory. This talk is intended to be accessible; all concepts from higher-dimensional category theory will be introduced in the talk.
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Nov 24 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Beilinson conjectures VI: a proof of cases of the Lichtenbaum conjecture.
Hicks Seminar Room J11
  Abstract:
This (possibly!!! -- see the abstract to Beilinson VII) final lecture in this semester's series on the Beilinson conjectures culminates with my ( AD 2000) proof of Lichtenbaum's conjecture for the order of $K_{4k}(Z)$. Mention will also be made of my new formula for the Borel- Beilinson regulator in dimension 3.
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Nov 25 Fri Mary-Jane Strong (Sheffield) Pure Maths Postgraduate Seminar
11:10 Splittings of cohomology theories
Hicks Seminar Room J11
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Nov 25 Fri David Jordan (Sheffield) Algebra / Algebraic Geometry seminar
14:05 Poisson algebras and modules: a case study III
Hicks Seminar Room J11
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Nov 25 Fri Neil Strickland (Sheffield)
14:10 Cobordism and formal power series
Lecture Room 6
  Abstract:
We will discuss the basic definitions of cobordism theory, and outline a proof of the following result of Thom: the unoriented cobordism ring $MO_*$ is given by $$ \mathbb{Z}/2[x_2,x_4,x_5,x_6,x_8,x_9,\ldots], $$ with one generator $x_k$ in each degree $k$ not of the form $2^i-1$. There will be many pretty pictures.
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Nov 29 Tue Ruben Sanchez (Sheffield) Topology Seminar
14:00 Equivariant K-homology for $SL(3,\mathbb{Z})$ and Coxeter groups
Hicks Seminar Room J11
  Abstract:
I will show how to compute the topological side of the Baum-Connes conjecture for $SL(3,\mathbb{Z})$ and some Coxeter groups. I will put some illustrative pictures.
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Nov 29 Tue Iakovos Androulidakis (Z)
16:10 Realisation of singular foliations by Lie groupoids
Hicks Seminar Room J11
  Abstract:
Lie groupoids generalise at the same time the notion of a Lie group and a manifold. Every Lie groupoid defines a foliation in a canonical way, which may well have singularities, and in this sense the groupoid can be thought of as a desingularization of this foliation. We address the converse problem in this talk, namely whether every singular foliation in the sense of Stefan and Sussmann comes from a Lie groupoid. In particular we present a construction that provides a positive answer, and discuss its implications in noncommutative geometry and quantization.
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Nov 30 Wed Dr Kiril Kuzanyan (Leeds) Applied Mathematics Colloquium
Helicity and Solar dynamo: confront theory and observations
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Nov 30 Wed Ivan Smith (Cambridge) Pure Maths Colloquium
16:00 Knots, matrices and symplectic topology
Hicks Seminar Room J11
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Dec 1 Thu Victor Snaith (Sheffield) Snaith seminar
12:10 Beilinson VII: Borel's regulator, the final mopping-up!!
Hicks Seminar Room J11
  Abstract:
I imagine that Beilinson VI will cover the Lichtenbaum conjecture but not the formula for Borel's regulator - so Beilinson VII is reserved for the latter, if necessary. It will be the last in the series!
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Dec 2 Fri Luis Hernandez-Hernandez (Sheffield) Pure Maths Postgraduate Seminar
11:10 Cohomology of Projective Bundles
Hicks Seminar Room J11
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Dec 2 Fri David Jordan (Sheffield) Algebra / Algebraic Geometry seminar
14:05 Possion algebras and modules: a case study IV
Hicks Seminar Room J11
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Dec 7 Wed Kari Ragnarsson (Aberdeen) Pure Maths Colloquium
16:00 Homotopy classifications of p-completed classifying spaces
Hicks Seminar Room J11
  Abstract:
In algebraic topology one typically applies powerful algebraic invariants to encode homotopy properties of topological spaces. In certain cases it is possible and useful to reverse this process by assigning a space to an algebraic object. An instance of this is the assignment to a finite group $G$ of a classifying space $BG$, whence the group $G$ can be recovered as the fundamental group. Furthermore, group homomorphisms between finite groups correspond bijectively to homotopy classes of maps between their classifying spaces. In this talk I will discuss how this correspondence changes when we focus on properties relative to a prime $p$. Topologically this means applying the $p$-completion functor to $BG$. I will present three classification theorems for $p$-completed classifying spaces of finite groups. First, the unstable classification, predicted by Martino- Priddy and proved by Oliver, which classifies the homotopy type of the $p$-completed classifying space of $G$ via the fusion system of $G$. Second, the stable classification, due to Martino-Priddy, which classifies the stable homotopy type of the p-completed classifying space of $G$ via weaker data, which loosely speaking can be regarded as a linearisation of the fusion system. Finally, the partially stable classification, which links the unstable and stable classifications. This is the surprising result that, by keeping track of inclusions of Sylow subgroups, the stable homotopy type of the $p$-completed classifying space of $G$ can again be classified via the fusion data of $G$. This classification also gives a simple description of maps realising stable homotopy equivalences (while preserving the inclusions of Sylow subgroups).
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Dec 9 Fri Yukinobu Toda (Tokyo) Algebra / Algebraic Geometry seminar
16:00 $A_{\infty}$ structures and Fourier-Mukai transforms (An introduction to A. Polishchuk's work)
Hicks Seminar Room J11
  Abstract:
First I will give an introduction of $A_{\infty}$ algebras and $A_{\infty}$ categories. Then we combine them with the techniques of Fourier-Mukai transforms, and approach the problem of describing Brill-Noether loci. These are generalizations of theta divisors of Jacobian of curves, and we will see that $A_{\infty}$ techniques can be applied to some classical problems in algebraic geometry.
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Dec 12 Mon Alfonso Gracia-Saz (Berkeley)
16:10 The symbol of a function of an operator (or How finding the right notation solves half the problem)
Hicks Seminar Room J11
  Abstract:
In the quantum description of a physical system, the observables (e.g. the energy) are represented by operators on a Hilbert space. In the classical description, they are represented by functions on phase space. Weyl quantization provides a bijection between quantum and classical observables. To every operator (quantum) $\widehat{A}$, we associate a function (classical) $A$, called its symbol. We consider the following problem. Let $\widehat{A}$ be an operator with symbol $A$ and let $f$ be a smooth function. Then $\widehat{B}:=f(\widehat{A})$ is another operator, with symbol $B$. What is $B$ in terms of $A$? We will provide an answer to this question in the form of a formula ``à la Feynman'', i.e. a power series whose terms are labeled by diagrams. This has various applications to quantum mechanics. No knowledge of physics will be assumed. The talk will come with a moral: There is no difficult calculation, only unfortunate notations.
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Dec 13 Tue Dr Fay Dowker (Blackett Laboratory, Imperial College) Applied Mathematics Colloquium
Causal Set Phenomenology
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Dec 13 Tue Halvard Fausk (Oslo) Topology Seminar
14:00 t-model structures
Hicks Seminar Room J11
  Abstract:
For every stable model category $M$ with a certain extra structure, we produce an associated model structure on the pro-category $Pro(M)$ and a spectral sequence, analogous to the Atiyah-Hirzebruch spectral sequence, with reasonably good convergence properties for computing in the homotopy category of $Pro(M)$. Our motivating example is the category of pro-spectra. The extra structure referred to above is a t-model structure. This is a rigidification of the usual notion of a t-structure on a triangulated category. A t-model structure is a proper simplicial stable model category $M$ with a t-structure on its homotopy category together with an additional factorization axiom.
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Dec 13 Tue Fay Dowker (Imperial College) Pure Maths Colloquium
16:00 Causal Set Phenomenology
Lecture Theatre G
  Abstract:
The hypothesis that the discrete substructure of spacetime is a causal set suggests a straightforward model building technique: invent phenomenological dynamics for matter (particles or fields) on a background causal set that is well approximated by our continuum spacetime. These models can be analysed to see if they predict observable eviations from continuum models. I will describe two examples of such models: "particle swerves" and a model of detector response to the scalar field of a scalar charge source.
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Dec 14 Wed Jon Woolf (Liverpool) Pure Maths Colloquium
16:00 Signatures and Witt spaces, or, why life is simpler with singularities.
Hicks Seminar Room J11
  Abstract:
The signature of a manifold is an important invariant: it is the basic obstruction to a manifold being the boundary of a manifold of one dimension higher. The talk will survey some classical results for computing signatures and explain how, by introducing a notion of signature for certain singular spaces, we can obtain very geometric proofs and significant extensions of these results.
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Jan 16 Mon Matthew Ando (Urbana-Champaign) Chromatic homotopy
16:00 TBA
Hicks Seminar Room J11
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Jan 23 Mon Ruben Sanchez (Sheffield) Chromatic homotopy
16:00 Orthogonal Spectra II
Hicks Seminar Room J11
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Jan 27 Fri Johann Sigurdsson (Sheffield) Chromatic homotopy
16:00 Structured Spectra
Hicks Seminar Room J11
  Abstract:
Now that we have good geometric models for the stable homotopy category it is time to construct spectra representing particular cohomology theories. The point is to do that in such a way that interesting structure of cohomology theories, such as pairings, is already reflected in structure on the spectra. I will in particular focus on the Thom spectra representing the various cobordism theories.
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Jan 30 Mon Johann Sigurdsson (Sheffield) Chromatic homotopy
16:00 Structured Spectra II
Hicks Seminar Room J11
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Feb 3 Fri Sam Marsh (Sheffield) Chromatic homotopy
16:00 Complex Oriented Cohomology Theories I
Hicks Seminar Room J11
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Feb 6 Mon Sam Marsh (Sheffield) Chromatic homotopy
16:00 Complex Oriented Cohomology Theories II
Hicks Seminar Room J11
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Feb 8 Wed Dr Thomas Neukirk (St Andrews) Applied Mathematics Colloquium
Current Build-up in Topologically Simple Magnetic Fields
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Feb 8 Wed Alexander Odesskii (Machester) Pure Maths Colloquium
16:00 Elliptic algebras
Hicks Seminar Room J11
  Abstract:
The talk is devoted to associative N-graded algebras presented by n generators and n(n-1)/2 quadratic relations and satisfying the so-called Poincare-Birkhoff-Witt condition (PBW-algebras). We consider examples of such algebras depending on two continuous parameters (namely, on an elliptic curve and a point on this curve) which are flat deformations of the polynomial ring in n variables. Diverse properties of these algebras will be described, together with their relations to integrable systems, deformation quantization, moduli spaces and other directions of modern investigations.
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Feb 10 Fri James Cranch (Sheffield) Chromatic homotopy
16:00 The Lazard Ring and Quillen's Theorem
Hicks Seminar Room J11
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Feb 13 Mon James Cranch (Sheffield) Chromatic homotopy
16:00 The Lazard Ring and Quillen's Theorem, II
Hicks Seminar Room J11
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Feb 15 Wed Prof Alexander B. Movchan (Liverpool) Applied Mathematics Colloquium
Asymptotic analysis of solutions to singularly perturbed problems in multi-structures
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Feb 15 Wed Victoria Hinchcliffe (Sheffield) Pure Maths Postgraduate Seminar
12:10 The Filter Dimension and the Inequality of Bernstein
Hicks Seminar Room J11
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Feb 15 Wed Nikita Markarian (Sheffield) Algebra / Algebraic Geometry seminar
14:00 Hochschild homology, Atiyah classes and Riemann-Roch theorem I
Hicks Seminar Room J11
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Feb 15 Wed Balazs Szendroi (Oxford) Pure Maths Colloquium
16:00 The amazing partition function of local P^1
Hicks Seminar Room J11
  Abstract:
To a manifold M, string theory associates its topological partition function, a finite dimensional approximation to a complicated path integral on M. One of the simplest cases when this function can be computed explicitly is that of local P^1, a certain complex threefold fibred over the projective line. Its partition function can be written in six or seven different ways, as infinite sum or infinite product, related to Gromov-Witten theory, Donaldson-Thomas theory, the combinatorics of partitions, Chern-Simons theory of knots... The talk will introduce these ideas in elementary terms.
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Feb 17 Fri Holger Brenner (Sheffield) Chromatic homotopy
16:00 Introduction to Algebraic Geometry
Hicks Seminar Room J11
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Feb 20 Mon David Gepner (Sheffield) Chromatic homotopy
16:00 Schemes, Sheaves and Topoi
Hicks Seminar Room J11
  Abstract:
We continue our introduction to derived algebraic geometry. In particular, we will define schemes, sheaves, and topoi (not necessarily in that order!) and, time permitting, consider possible homotopy-theoretic generalizations.
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Feb 22 Wed Prof Roger Grimshaw (Loughborough) Applied Mathematics Colloquium
Internal solitary waves and undular bores in the atmosphere and ocean
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Feb 22 Wed Zacky Choo (Sheffield) Pure Maths Postgraduate Seminar
12:10 Borel's Regulator
Hicks Seminar Room J11
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Feb 22 Wed Nikita Markarian (Sheffield) Algebra / Algebraic Geometry seminar
14:00 Hochschild homology, Atiyah classes and Riemann-Roch theorem II
Hicks Seminar Room J11
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Feb 22 Wed Alastair King (University of Bath) Pure Maths Colloquium
16:00 Moduli of sheaves from moduli of Kronecker modules
Hicks Seminar Room J11
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Feb 24 Fri David Gepner (Sheffield) Chromatic homotopy
16:00 Schemes, Sheaves and Topoi II
Hicks Seminar Room J11
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Mar 1 Wed Dr Andrew Soward (Exeter) Applied Mathematics Colloquium
Non-axisymmetric $\alpha^2\Omega$-dynamo waves in thin stellar shells
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Mar 1 Wed Alastair Hamilton (University of Bristol) Pure Maths Colloquium
16:00 Graph homology classes via infinity-algebras
Hicks Seminar Room J11
  Abstract:
I will discuss the role played by certain aspects of quantum field theory such as the Feynman calculus and the Batalin-Vilkovisky formalism in the construction of graph homology and cohomology classes, as introduced by Kontsevich in his 92/93 papers. I will also give the first example of a nontrivial pairing between a graph homology and cohomology class which arises from the evaluation of a super-integral, more than ten years since the idea was first proposed by Kontsevich.
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Mar 3 Fri David Gepner (Sheffield) Chromatic homotopy
16:00 The Functor of Points Approach to Algebraic Geometry
Hicks Seminar Room J11
  Abstract:
We will illustrate our ``functor of points'' approach to algebraic geometry through a number of concrete examples. In particular, we will see when a subfunctor of a scheme is itself a (closed or open) subscheme, and we will determine the functor represented by n-dimensional projective space.
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Mar 6 Mon David Gepner (Sheffield) Chromatic homotopy
16:00 Quasicoherent Sheaves
Hicks Seminar Room J11
  Abstract:
We will introduce the notion of a (quasi)coherent sheaf on a scheme. The (quasi)coherent sheaves play a central role in algebraic geometry, particularly in cohomology theory. We will illustrate with examples of coherent sheaves on projective space.
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Mar 8 Wed Dr Robert Walsh (Central Lancashire) Applied Mathematics Colloquium
Taking the Sun's temperature: modelling the pros and cons of EUV rastering spectrometers vs narrow-band imagers
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Mar 8 Wed Marc Lackenby (Oxford) Pure Maths Colloquium
16:00 Property tau
Hicks Seminar Room J11
  Abstract:
How can one construct computer networks without bottlenecks? Is there a method of efficiently shuffling a pack of cards? How does the spectrum of the Laplacian on a manifold behave under finite-sheeted covers? How can one detect `large' groups? Do hyperbolic 3-manifolds contain essential surfaces? In my talk, I will show how these questions are all related to an intriguing concept known as `Property tau'.
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Mar 9 Thu Holger Brenner (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Grothendieck topologies and closure operations for ideals I
Hicks Seminar Room J11
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Mar 10 Fri David Gepner (Sheffield) Chromatic homotopy
16:00 Quasicoherent Sheaves
Hicks Seminar Room J11
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Mar 13 Mon Ieke Moerdijk (Sheffield) Chromatic homotopy
16:00 Operads, Dendroidal Sets and Weak Categories
Hicks Seminar Room J11
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Mar 15 Wed Prof Leo Brevdo (University of the Mediterranean (Marseille, France)) Applied Mathematics Colloquium
Absolute instability of spatially developing flows and media
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Mar 15 Wed Bruce Bartlett (Sheffield) Pure Maths Postgraduate Seminar
12:10 2-representations of groups
Hicks Seminar Room J11
  Abstract:
There is a jigsaw puzzle P of closely related ideas that revolve around topological quantum field theory, n- categories, gerbes, elliptic cohomology, knot theory, and higher gauge theory. Unfortunately, I am not qualified to talk about P. I will however attempt to address one infinitesimal piece of P, which is called the "2-category of 2-representations of a finite group.
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Mar 15 Wed Jonathan Jordan (University of Sheffield, dept. of Probability and Statistics) Pure Maths Colloquium
16:00 Spectral properties of fractal graphs
Hicks Seminar Room J11
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Mar 16 Thu Holger Brenner (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Grothendieck topologies and ideal closure operations II
Hicks Seminar Room J11
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Mar 17 Fri Ruben Sanchez (Sheffield) Chromatic homotopy
16:00 Homotopy Limits and Colimits
Hicks Seminar Room J11
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Mar 20 Mon Ieke Moerdijk (Sheffield) Chromatic homotopy
16:00 Operads, Dendroidal Seta and Weak Categories.
Hicks Seminar Room J11
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Mar 22 Wed James Cranch (Sheffield) Pure Maths Postgraduate Seminar
12:10 Rational Morava E-theory of symmetric groups
Hicks Seminar Room J11
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Mar 22 Wed Frances Kirwan (Oxford) Pure Maths Colloquium
16:00 Moduli spaces of bundles over curves revisited
Hicks Seminar Room J11
  Abstract:
Several decades ago the Betti numbers of the moduli spaces of stable vector bundles (with fixed mutually coprime rank and degree) over a Riemann surface were found, first by Harder and Narasimhan using number-theoretic methods and counting objects defined over finite fields, and soon after by Atiyah and Bott using Yang-Mills theory and equivariant Morse theory. This talk will link these two approaches and describe some more recent results on the geometry of the moduli spaces.
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Mar 23 Thu Holger Brenner (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Grothendieck topologies and ideal closure operations III
Hicks Seminar Room J11
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Mar 24 Fri Ruben Sanchez (Sheffield) Chromatic homotopy
16:00 Homotopy Limits and Colimits, II
Hicks Seminar Room J11
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Mar 27 Mon Ieke Moerdijk (Sheffield) Chromatic homotopy
16:00 Operads, dendroidal sets and weak categories III
Hicks Seminar Room J11
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Mar 29 Wed Dr Jacques Vanneste (Edinburgh) Applied Mathematics Colloquium
Wave radiation by slow flows
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Mar 29 Wed Almar Kaid (Sheffield) Pure Maths Postgraduate Seminar
12:10 Syzygy Bundles and the Weak Lefschetz Property
Hicks Seminar Room J11
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Mar 29 Wed Tom Leinster (Glasgow) Pure Maths Colloquium
16:00 Another look at Euler characteristic
Hicks Seminar Room J11
  Abstract:
Far beyond the realm where we can count "vertices minus edges", there are spaces that, nevertheless, appear to have a well- defined Euler characteristic. For example, the Julia set of any rational function f seems to have an Euler characteristic, a number giving basic information about the dynamical behaviour of f. But to define the Euler characteristic of such spaces, we first need to define the Euler characteristic of a category. This involves generalizing the Mobius inversion formula of classical number theory. We'll see, for instance, that the Euler characteristic of the category of finite sets and bijections is e = 2.718... . Throughout, our motto is: "Euler characteristic is generalized cardinality".
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Mar 31 Fri Ruben Sanchez (Sheffield) Chromatic homotopy
16:00 Homotopy Limits and Colimits III
Hicks Seminar Room J11
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Apr 26 Wed Dr Dave Roscoe (Sheffield) Applied Mathematics Colloquium
Redshift phenomenology: A review of Napier's analysis
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Apr 26 Wed Caroline Series (Warwick) Pure Maths Colloquium
16:00 Taming the unruly hyperbolic jungle
Hicks Seminar Room J11
  Abstract:
The last few years have seens some spectacular developments in our understanding of hyperbolic 3-manifolds. The title of my talk is taken from a recent article in Science magazine on this topic. The problems are equivalent to much simpler sounding questions about what happens when you iterate Mobius maps. I will give an overview of the background and the significance of the new developments, illustrated with many pictures from our book Indra's Pearls (Mumford, Series and Wright, CUP 2002).
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Apr 27 Thu Georg Struth (Sheffield, Department of Computer Science) Algebra / Algebraic Geometry seminar
15:10 Kleene algebras and program analysis
Hicks Seminar Room J11
  Abstract:
Kleene algebras are non-commutative idempotent semirings with an additional operation for iteration or reflexive transitive closure. They have recently received considerable attention as foundational structures in computer science and for their suitability in different application areas. In this talk I will discuss the basics of Kleene algebras and related structures. I will also try to point out the general benefits of algebraic approaches to software analysis and verification and survey a number of applications in the analysis of programs and software systems.
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Apr 28 Fri James Cranch (Sheffield) Chromatic homotopy
16:00 Introduction to Stacks
Hicks Seminar Room J11
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May 2 Tue Neil Dummigan (Sheffield)
11:00 Number Theory Seminar "Modular degrees of elliptic curves"
Hicks Seminar Room J11
  Abstract:
In the first talk I'll look at Neron models of abelian varieties, the Tate p-adic uniformisation of elliptic curves and the modular parametrisations of elliptic curves over the rationals. In the second talk I'll look at the description of the special fiber of the Neron model of the Jacobian of a curve, in terms of the special fiber of a regular model of the curve. Then I'll use all this to prove something about the degrees of modular parametrisations.
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May 3 Wed Dr Sergei Molokov (Coventry) Applied Mathematics Colloquium
Interfacial instability in a two-layer system with transverse electric current
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May 3 Wed Rajender Adibhatla (Sheffield) Pure Maths Postgraduate Seminar
12:10 Deformations of Galois representations
Hicks Seminar Room J11
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May 3 Wed Simon Donaldson (Imperial College) Pure Maths Colloquium
16:00 Differential geometry on toric varieties
Hicks Seminar Room J11
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May 5 Fri James Cranch (Sheffield) Chromatic homotopy
16:00 Introduction to Stacks, II
Hicks Seminar Room J11
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May 8 Mon James Cranch (Sheffield) Chromatic homotopy
16:00 Introduction to Stacks, III
Hicks Seminar Room J11
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May 10 Wed Prof Basil Hiley (Birkbeck College) Applied Mathematics Colloquium
Quantum Field Theory and the Bohm Model: the Role of the Photon
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May 10 Wed Anthony Hignett (Sheffield) Pure Maths Postgraduate Seminar
12:10 Stable cooperations in complex K-theory
Hicks Seminar Room J11
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May 10 Wed Fran Burstall (Bath) Pure Maths Colloquium
16:00 Harmonic Gauss maps
Hicks Seminar Room J11
  Abstract:
I shall give an overview for non-experts of the modern theory of harmonic maps and how it applies to questions of classical (and sometimes unfashionable) differential geometry via an appropriate notion of Gauss map.
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May 12 Fri James Cranch (Sheffield) Chromatic homotopy
16:00 Introduction to Stacks, IV
Hicks Seminar Room J11
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May 15 Mon David Gepner (Sheffield) Chromatic homotopy
16:00 Higher and Derived Stacks, I
Hicks Seminar Room J11
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May 16 Tue Paul Buckingham (Sheffield)
11:00 TBA - this will be a number theory seminar
Hicks Seminar Room J11
  Abstract:
This talk will deal with the annihilator ideal of the group ring of a Galois group action on a cyclotomic class group.
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May 17 Wed Prof Chris Eilbeck (Heriot Watt) Applied Mathematics Colloquium
Breathers in discrete systems
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May 17 Wed Panagiotis Tsaknias (Sheffield) Pure Maths Postgraduate Seminar
12:10 Modular forms and Fermat's Last Theorem
Hicks Seminar Room J11
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May 18 Thu Rodney Sharp (Sheffield) Algebra / Algebraic Geometry seminar
15:00 Artinian modules with a Frobenius action or What I did in my Study Leave
Hicks Seminar Room J11
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May 18 Thu Luca Stefanini (Zurich)
16:00 Differential Geometry Seminar Integration of LA-Groupoids
Hicks Seminar Room J11
  Abstract:
Many problems regarding second order differential geometry, Poisson geometry, Lie algebroids and Lie groupoids can be formulated in terms of double structures such as double Lie groupoids, LA-groupoids and double Lie groupoids.

After overviewing the key facts in Lie theory for Lie algebroids and Lie groupoids, it shall be presented how Lie's theorems extend for LA-groupoids and double Lie groupoids. Apart from a few technicalities, the suitable generalisations are obtained using simple functorial arguments. A few applications to integrability and duality of Poisson groupoids will be briefly described.

Note added by Kirill : An LA-groupoid is a groupoid object in the category of Lie algebroids. These structures arise by infinitesimalizing double Lie groupoids, but they also arise in nature as the cotangent bundles of Poisson Lie groups. In that case, they are intermediate between the Drinfel'd double of the corresponding Lie bialgebra and the matched pairs of Lie groups, or symplectic double groupoids, which provide global forms of Poisson Lie groups.

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May 19 Fri David Gepner (Sheffield) Chromatic homotopy
16:00 Higher and Derived Stacks, II
Hicks Seminar Room J11
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May 24 Wed Dr David Roscoe (Sheffield) Applied Mathematics Colloquium
Electrodynamics: Old theory in a new light
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May 26 Fri David Gepner (Sheffield) Chromatic homotopy
16:00 Higher and Derived Stacks, III
Hicks Seminar Room J11
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Jun 1 Thu Dr Manuel Blickle (Essen) Algebra / Algebraic Geometry seminar
15:00 Witt-rational singularities and rational points
Hicks Seminar Room J11
  Abstract:
I am reporting on joint work with Hélène Esnault. In this talk I will outline the basic properties of a newly introduced class of singularities for varieties in positive characteristic, called Witt-rational singularites. I will attempt to explain how this notion naturally arises in the context of generalizing results on congruences of rational points of a smooth variety over a finite field beyond the smooth case. In fact, our main result roughtly states that a Witt-rational and rationally connected variety has a rational point. Examples of (non) Witt-rational varieties will be discussed as well as the relation of Witt-rational to a Hodge-theoretic consequence of rational singularities in characteristic zero.
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Jun 6 Tue Bertrand Toen (Toulouse) GATA Seminar
15:00 Stacks and derived categories I
Hicks Seminar Room J11
  Abstract:
The purpose of these two talks is to report on recent works which use stack theory to study derived categories.

In the first talk I will discuss the problem of constructing a reasonable moduli space for compact objects in a given triangulated category (or rather a triangulated ``dg-category''). In a first part I will explain some motivations coming from algebraic geometry and representation theory (e.g. the contruction of moduli spaces of complexes of sheaves on an algebraic variety, the definition of ``Hall algebras'' for derived categories). The second part of the talk will be devoted to present a solution to this problem using a notion of ``derived $\infty$-stack'': the main theorem states that the (derived $\infty$-) stack of compact objects in a given ``saturated'' dg-category is algebraic. Some corollaries and possible future applications will be discussed.
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Jun 7 Wed Bertrand Toen (Toulouse) GATA Seminar
15:00 Stacks and derived categories II
Hicks Seminar Room J11
  Abstract:
The second talk is concerned with the problem of constructing a reasonable moduli space for triangulated (dg)-categories themselves.

The main theorem of this second talk states that the (derived $\infty$-) stack of ``saturated dg-categories'' is algebraic. The infinitesimal theory of this moduli stack can be used to explain the relation between the deformation theory of dg-categories and Hochschild cohomology. Two other applications will be discussed. To start with I will describe, for any given rational number p/q, a circle action on the moduli stack of saturated dg-categories whose fixed points are ``Calabi-Yau dg-categories of dimension p/q''. This can be used to prove that the deformation theory of Calabi-Yau dg-categories is controlled by cyclic cohomology. Finally, I will explain how the ``period map'', from the stack of varieties to the stack of saturated dg-categories, can be used to study derived equivalence classes of algebraic varieties.
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Jun 14 Wed Dr Leon Ofman (NASA, USA) Applied Mathematics Colloquium
Waves in coronal active regions: observations and models
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Sep 27 Wed Christian Elsholtz (Royal Holloway) Pure Maths Colloquium
16:00 Combinatorial prime number theory
Hicks Seminar Room J11
  Abstract:
In this talk we study combinatorial questions about primes. In particular, Ostmann asked whether there exist two sets A and B (with at least two elements each) so that their sumset A+B equals the set of primes, for sufficiently large primes. Using a new version of the large sieve method we show, that such sets A and B would need to have counting functions of size $N^{1/2 +o(1)}$, whereas previously only a lower bound of $N^{o(1)}$ and an upper bound of $N^{1+o(1)}$ was known. This implies, for example, that the set of primes cannot be decomposed into three such sets. This talk will give a nontechnical survey of the underlying ideas and show how a new type of the large sieve method and combinatorial counting arguments (including graph theory) can be applied to such problems. Other recent work on primes by Green, Tao, Goldston, Pintz and Yildirim will be mentioned
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Oct 4 Wed Prof. Valentina Zharkova (Bradford) Applied Mathematics Colloquium
On the origin of three seismic sources in the 28 October 2003 flare
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Oct 5 Thu John Fry (Sheffield) Statistics Seminar
14:00 The Mathematics of Financial Crashes
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Oct 5 Thu Keith Harris (Sheffield) Statistics Seminar
14:00 Statistical Modelling and Inference for Radio-Tracking.
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Oct 5 Thu Holger Brenner (Sheffield) Topology Seminar
15:10 Continuous solutions to algebraic forcing equations
Hicks Seminar Room J11
  Abstract:
Let $f_1$, ..., $f_n$ and $f$ be polynomials in $C[X_1,...,X_m]$. When is it possible to write $f = q_1f_1 + ... + q_nf_n$ with continuous functions $q_i: C^m \to C$ ($C$=complex numbers). Does there exists an algebraic characterization of this property? The set of polynomials $f$ which can be written in this way form an ideal which we call the continuous closure of $(f_1,...,f_n)$. We give exclusion and inclusion criteria for this closure operation and algebraic apporoximations, in particular in terms of the axes closure (to be introduced). In the case of a monomial ideal we show that the continuous closure and the axes closure have the same combinatorial description and coincide.
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Oct 10 Tue Burt Totaro (Cambridge) Topology Seminar
14:00 The geometry of Hilbert's fourteenth problem
Hicks Seminar Room J11
  Abstract:
All kinds of classification problems in geometry (going back to Euclid) lead to the problem of finding the ring of polynomial invariant functions for a group acting on a vector space. Hilbert asked whether rings of invariants are always finitely generated. The answer is yes in many cases but no in general, by Nagata. Although the problem is formulated algebraically, Nagata's counterexamples make brilliant use of the geometry of algebraic curves. I will present the latest advances on the problem.
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Oct 11 Wed Andy Tonks (London Metropolitan University) Pure Maths Colloquium
16:00 On $K_1$ (and $K_0$) of a Waldhausen category
Hicks Seminar Room J11
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Oct 12 Thu David Jordan (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Poisson brackets on $\mathbb{C}[x,y,z]$
Hicks Seminar Room J11
  Abstract:
The talk will offer various elementary observations on Poisson brackets on $A:=\mathbb{C}[x,y,z]$. Apparently it is of interest to (some) physicists to know when the sum of two Poisson brackets is again a Poisson bracket, in which case the two are said to be compatible. We consider two types of Poisson brackets on $A$, one (which I call exact) depending on one polynomial $F\in A$ and the other (proximate) depending on two such polynomials $G$ and $H$. Here proximate with $H=1$ is exact. The criterion for one exact and one proximate bracket to be compatible turns out to be symmetric in $F, G, H$. Hopefully someone in the audience will point out why this is geometrically obvious! I will then consider how close sums of these compatible pairs come to giving all Poisson brackets on $A$, referring to an existing classification of quadratic Poisson brackets on $A$. Maybe there will be a vague conjecture. Time permitting, I will look at Poisson brackets that restrict to the zero bracket on $B:=\mathbb{C}[x,y]$ and their connection with simple rings of formal differential operators on $B$.
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Oct 18 Wed Prof Dugald Duncan (Heriot-Watt) Applied Mathematics Colloquium
Numerical analysis of a convolution model of phase separation
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Oct 18 Wed Alexey Bondal (Steklov Mathematics Institute) Pure Maths Colloquium
16:00 Noncommutative deformations of algebraic varieties and Poisson brackets.
Hicks Seminar Room J11
  Abstract:
The first part of the talk will be a short survey on possible approaches to and results on noncommutative deformations of algebraic verieties, in particular, projective spaces. In the second part we will discuss results and conjectures on the geometric structure of Poisson brackets on Fano varieties.
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Oct 19 Thu Neil Dummigan (Sheffield) Pure Maths Postgraduate Seminar
12:10 Euler and the zeta function
Hicks Seminar Room J11
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Oct 19 Thu Andrew Stacey (Sheffield) Algebra / Algebraic Geometry seminar
15:10 A Plethora of Plethories - Describing Unstable Cohomology Operations
Lecture Theatre 7
  Abstract:
Generalised cohomology theories are a useful tool that allow topologists to use algebraic techniques to study topological spaces. One of the bits of baggage that comes with a generalised cohomology theory is the set of operations on said theory. There are several different ways of describing the algebraic structure of a set of operations which vary from the "neat" to the "useful" via the "completely bizarre"; most are described in a paper by Boardman, Johnson, and Wilson in the Handbook of Algebraic Topology. I shall explain some of these descriptions and introduce another one which appears not to have been considered in this context. It uses the notion of a "plethory", which was originally defined (though not by that name) in the 70s by Tall and Wraith.
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Oct 25 Wed Dr Rony Keppens (K.U.Leuven) Applied Mathematics Colloquium
Grid-adaptive approaches for computing magnetized plasma dynamics
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Oct 25 Wed John Power (University of Edinburgh) Pure Maths Colloquium
16:00 The Algebra of Computational Effects
Hicks Seminar Room J11
  Abstract:
Lawvere theories and monads have been the two main category theoretic formulations of universal algebra, Lawvere theories arising in 1963 and the connection with monads being established a few years later. Monads, although mathematically the less direct and less malleable formulation, rapidly gained precedence. A generation later, Eugenio Moggi instigated the use monads in theoretical computer science in order to model computational effects, without reference to universal algebra. But since then, the relevance of universal algebra to computational effects has been recognised, leading to renewed prominence of the notion of Lawvere theory, now in a computational setting. Here, we investigate the history, in particular asking why Lawvere theories were eclipsed by monads in the 1960's, and how the renewed interest in them in a computer science setting has been developing and might continue to develop in future.
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Oct 26 Thu Nikita Markarian (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Non-abelian Hodge theory in characteristic 0 and p>0"
Hicks Seminar Room J11
  Abstract:
We shall give a short review of the non-abelian Hodge theory as it was introduces in works of Deligne, Simpson and others. Then we shall discuss a possible analog of it (for curves) in positive characteristic.
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Oct 31 Tue Victor Snaith (Sheffield) Topology Seminar
14:00 Upper Triangle Technology and the Arf Invariant
Hicks Seminar Room J11
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Nov 1 Wed Dr John Barrett (Nottingham) Applied Mathematics Colloquium
Geometry of the standard model and neutrino mass terms
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Nov 1 Wed Paul Turner (Heriot-Watt) Pure Maths Colloquium
16:00 Khovanov homology for links
Hicks Seminar Room J11
  Abstract:
Khovanov homology is a vector space valued invariant of links whose graded Euler characteristic is the Jones polynomial. It is a stronger invariant than the Jones polynomial, reveals interesting further structure and has nice functorial properties with respect to link cobordisms. In this talk I will endeavour to give an overview of the subject discussing definitions, elementary properties and some applications.
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Nov 2 Thu Nancy Nicholls (Reading) Statistics Seminar
14:00 Getting Started: Data Assimilation for Very Large Inverse Problems in Environmental Science
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Nov 2 Thu David Stern (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Exceptional collections and mutations on Del Pezzo surfaces.
Hicks Seminar Room J11
  Abstract:
Abstract: This talk will use special collections of bundles to obtain abelian categories that are derived equivalent to the category of coherent sheaves of a Del Pezzo surface. These abelian categories are the categories of modules of the homomorphism algebra of bundles in the collection which can be described as the path algebra of a quiver. These constructions work on strong exceptional collections and the main focus of the talk will be to describe an operation, called mutation, acting on a closed set of such collections.
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Nov 7 Tue Alastair Craw (Glasgow) Topology Seminar
14:00
Hicks Seminar Room J11
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Nov 8 Wed Dr Yasmin Andrew (JET (Culham)) Applied Mathematics Colloquium
Experimental Studies of the L-H Transition on JET
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Nov 8 Wed Alastair Craw (University of Glasgow) Pure Maths Colloquium
16:00
Hicks Seminar Room J11
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Nov 9 Thu Clive Anderson (Sheffield) Statistics Seminar
14:00 Some Extreme Value Problems in Metal Fatigue
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Nov 13 Mon Mikhail Kapranov (Yale University) GATA Seminar
14:00 Talk 1: "Spaces of formal loops and gerbes of chiral differential operators"
Hicks Seminar Room J11
  Abstract:
For a complex manifold X physics considerations lead to a construction of certain sheaves of vertex algebras on X called chiral differential operators (CDO). While locally such a sheaf is unique, globally the situation is similar to that of spinor bundles on a Riemannian manifold. In the categorical terminology they form a gerbe. We relate this gerbe with the gerbe describing 'determinantal anomaly' for the space of free loops in X. The calculation of the class of the gerbe of CDO due to Gorbounov, Malikov and Schechtman turns out to be a particular case of a local Riemann-Roch-type theorem for determinantal gerbes.
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Nov 14 Tue Neil Strickland (Sheffield) Topology Seminar
14:00 Structured ring spectra and the nilpotence theorem
Hicks Seminar Room J11
  Abstract:
One form of the nilpotence theorem says that if $R$ is a ring spectrum and $a\in\pi_dR$ maps to zero in $MU_dR$ then $a^n=0$ for large $n$. This is a very powerful result, which forms the basis for a huge body of work in stable homotopy theory. Strangely, however, little further work has been done with the circle of ideas used in the proof of the nilpotence theorem. In this talk we will revisit these ideas using some newer technology of structured ring spectra.
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Nov 15 Wed Dr Konstantin Ilin (York) Applied Mathematics Colloquium
The stability of tangential and rotational discontinuities in MHD
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Nov 15 Wed Peter Jorgensen (Newcastle) Pure Maths Colloquium
16:00 Interactions between algebra, analysis, and topology
Hicks Seminar Room J11
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Nov 16 Thu David Scott (Auckland) Statistics Seminar
14:00 The hyperbolic and related distributions: problems of implementation
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Nov 16 Thu Mikhail Kapranov (Yale University) GATA Seminar
15:10 Talk 2: "Spaces of formal loops and gerbes of chiral differential operators."
Hicks Seminar Room J11
  Abstract:
For a complex manifold X physics considerations lead to a construction of certain sheaves of vertex algebras on X called chiral differential operators (CDO). While locally such a sheaf is unique, globally the situation is similar to that of spinor bundles on a Riemannian manifold. In the categorical terminology they form a gerbe. We relate this gerbe with the gerbe describing 'determinantal anomaly' for the space of free loops in X. The calculation of the class of the gerbe of CDO due to Gorbounov, Malikov and Schechtman turns out to be a particular case of a local Riemann-Roch-type theorem for determinantal gerbes.
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Nov 21 Tue Mikhail Kapranov (Yale University) GATA Seminar
14:00 Talk 3: "Spaces of formal loops and gerbes of chiral differential operators."
Hicks Seminar Room J11
  Abstract:
For a complex manifold X physics considerations lead to a construction of certain sheaves of vertex algebras on X called chiral differential operators (CDO). While locally such a sheaf is unique, globally the situation is similar to that of spinor bundles on a Riemannian manifold. In the categorical terminology they form a gerbe. We relate this gerbe with the gerbe describing 'determinantal anomaly' for the space of free loops in X. The calculation of the class of the gerbe of CDO due to Gorbounov, Malikov and Schechtman turns out to be a particular case of a local Riemann-Roch-type theorem for determinantal gerbes.
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Nov 22 Wed Dr Lisa Hall (Sheffield) Applied Mathematics Colloquium
Consistent modified gravity models
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Nov 22 Wed Samir Siksek (University of Warwick) Pure Maths Colloquium
16:00 Classical Diophantine Equations and the Proof of Fermat's Last Theorem
Hicks Seminar Room J11
  Abstract:
Wiles' proof of Fermat's Last Theorem is one of the happiest memories of the 20th century. Unfortunately, Wiles' proof does not readily extend in a way that allows us to solve many other classical Diophantine problems. In this talk, based on joint work with Bugeaud and Mignotte, we explain how the proof of Fermat's Last Theorem can be combined with older analytic techniques due to Baker, in a way that solves several classical Diophantine problems. For example, we show that the only perfect powers in the Fibonacci sequences are 0, 1, 8, 144.
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Nov 23 Thu Stuart Barber (Leeds) Statistics Seminar
14:00 Signal processing using complex Daubechies wavelets
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Nov 23 Thu Konstantin Ardakov (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Iwasawa algebras
Hicks Seminar Room J11
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Nov 29 Wed Dr Duncan Mackay (St. Andrews) Applied Mathematics Colloquium
MHD Simulations of Solar Prominences
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Nov 29 Wed Herbert Gangl (University of Durham) Pure Maths Colloquium
16:00 Multiple polylogarithms, polygons and algebraic cycles.
Hicks Seminar Room J11
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Nov 30 Thu David Barnes (Sheffield) Pure Maths Postgraduate Seminar
12:10 Categories with Involution
Hicks Seminar Room J11
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Nov 30 Thu Goran Peskir (Manchester) Statistics Seminar
14:00 Optimal stopping
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Nov 30 Thu Konstantin Ardakov (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Iwasawa algebras II
Hicks Seminar Room J11
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Dec 5 Tue Andrew Ranicki (Edinburgh) Topology Seminar
14:00 The geometric Hopf invariant
Hicks Seminar Room J11
  Abstract:
The talk will be a report on an ongoing joint project with Michael Crabb (Aberdeen). The geometric Hopf invariant of a stable map $F:\Sigma^{\infty}X \to \Sigma^{\infty}Y$ is a stable $Z_2$-equivariant map $h(F):X \to (S^{\infty})^+\wedge(Y \wedge Y)$ to the quadratic construction on $Y$. The stable $Z_2$-equivariant homotopy class of $h(F)$ is the primary obstruction to desuspending $F$. The geometric Hopf invariant of the stable Umkehr map $F:\Sigma^{\infty}M^+ \to \Sigma^{\infty}T(\nu_f)$ of an immersion $f:N^n\to M^m$ of manifolds factors through the $Z_2$-equivariant double point set of $f$. The $\pi_1$-equivariant version of the geometric Hopf invariant has an application to Wall's non-simply-connected surgery theory.
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Dec 6 Wed Toby Stafford (University of Michigan) Pure Maths Colloquium
16:00 Noncommutative Projective Surfaces
Hicks Seminar Room J11
  Abstract:
Noncommutative projective geometry seeks to use the intuition and techniques from classical projective algebraic geometry to understand the structure of noncommutative algebras and related modules categories. In this talk I will survey some of the basic ideas and techniques in the subject and, time permitting, outline recent work that describes a large class of ``noncommutative surfaces'' which have some weird and wonderful properties.
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Dec 7 Thu Raj Bhansali (Liverpool) Statistics Seminar
14:00 Frequency Analysis of Chaotic Intermittency Maps with Slowly Decaying Correlations
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Dec 12 Tue Simon Willerton (Sheffield) Topology Seminar
14:00 Hopf Monads
Hicks Seminar Room J11
  Abstract:
Representations of finite groups have various nice properties, you can tensor two representations together to get another representation and you can take the dual of a representation to get a new representation. This makes the category of representations into a `monoidal category with duals' which lifts these structures from the category of vector spaces. More generally this is true of the representations of any Hopf algebra. A monad is a categorical gadget which can be viewed as generalization of an algebra (in a sense I will explain), and which has a category of representations. Motivated by some specific examples you can ask when the category of representations is a monoidal category with duals (ie when the monad is a *Hopf* monad). I will endeavour to explain my pictorial approach to the answer given by Bruguiere and Virilizier.
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Dec 13 Wed Prof Koji Ohkitani (Sheffield) Applied Mathematics Colloquium
Blowup and regularity problems of hypoviscous fluid equations.
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Dec 13 Wed Paul Smith (University of Washington) Pure Maths Colloquium
16:00 Noncommutative Hirzebruch surfaces
Hicks Seminar Room J11
  Abstract:
I will introduce the audience to some of the main ideas and methods in non-commutative algebraic geometry by focusing on a rich class of examples, the spaces of the title, and showing how closely their behavior follows that in the commutative case. Our results about non-commutative Hirzebruch surfaces, $qF_n$, specialize to the commutative case: for example, there is a map, in the sense of non-commutative geometry, to the projective line, there is a curve on $qF_n$ with self-intersection number (defined in terms of the Euler form on the Grothendieck group) $-n$, and contracting that curves provides maps to other well-known non-commutative surfaces that are again analogues of their commutative counterparts. The starting point for the definition and analysis is a non-commutative analogue of Cox's homogeneous coordinate ring of a toric variety.
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Dec 14 Thu Stefanie Biedermann (Southampton) Statistics Seminar
14:00 Robust optimal designs for dose-response experiments
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Dec 14 Thu Sukhendu Mehrotra (Sheffield) Algebra / Algebraic Geometry seminar
15:10 Stability Manifolds as Extended Kaehler Moduli Spaces
Hicks Seminar Room J11
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Jan 15 Mon Sarah Whitehouse (Sheffield) Chromatic homotopy
14:00 Topological Hochschild Homology
Hicks Seminar Room J11
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Feb 7 Wed Jitesh S.B. Gajjar (Manchester) Applied Mathematics Colloquium
16:00 Global stability calculations of some separated flows
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Feb 7 Wed Kevin Buzzard (Imperial College London) Pure Maths Colloquium
16:15 Artin's conjecture on L-functions
Hicks Seminar Room J11
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Feb 8 Thu Elke Thonnes (University of Warwick) Statistics Seminar
14:00 Statistical analysis of pore patterns in fingerprints
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Feb 14 Wed Ivan Fesenko (Nottingham) Pure Maths Colloquium
16:00 Dealing with noncommutative aspects of 1d number theory in a commutative 2d way
Hicks Seminar Room J11
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Feb 14 Wed Rich Kerswell (Bristol) Applied Mathematics Colloquium
16:00 Transition to Turbulence in a Pipe
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Feb 16 Fri Neil Dummigan (Sheffield) Algebra / Algebraic Geometry seminar
14:10 p-adic Hodge theory I
Hicks Seminar Room J11
  Abstract:
Global and local Galois groups, Frobenius elements, cyclotomic characters, Tate modules of elliptic curves.
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Feb 20 Tue John Greenlees (Sheffield) Topology Seminar
14:00 Rational cohomology theories on free $G$-spaces
Hicks Seminar Room J11
  Abstract:
I aim to describe a classification for the theories of the title. More precisely, they are classified by free rational $G$-spectra, and I will describe an algebraic model when $G$ is a connected compact Lie group (the category of torsion modules over the polynomial ring $H^*(BG;Q)$). The two ingredients are an Adams spectral sequence and derived Morita theory. (Joint work with Brooke Shipley).
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Feb 21 Wed Silvia Dalla (Manchester) Applied Mathematics Colloquium
16:00 Solar science with AstroGrid
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Feb 22 Thu Almar Kaid Pure Maths Postgraduate Seminar
12:10 Detecting semistability of vector bundles on curves
Hicks Seminar Room J11
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Feb 22 Thu Ed Cripps (Sheffield) Statistics Seminar
14:00 Variable selection and covariance selection in multivariate Gaussian linear regression
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Feb 27 Tue John Greenlees (Sheffield) Topology Seminar
14:00 Rational cohomology theories on free $G$-spaces pt II
Hicks Seminar Room J11
  Abstract:
I aim to describe a classification for the theories of the title. More precisely, they are classified by free rational $G$-spectra, and I will describe an algebraic model when $G$ is a connected compact Lie group (the category of torsion modules over the polynomial ring $H^*(BG;Q)$). The two ingredients are an Adams spectral sequence and derived Morita theory. (Joint work with Brooke Shipley).
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Feb 28 Wed Tony Arber (Warwick) Applied Mathematics Colloquium
16:00 Emergence of flux through into the Solar corona: the effect of partially ionized layers
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Feb 28 Wed Meinolf Geck (Aberdeen) Pure Maths Colloquium
16:15 Representations of Hecke algebras
Hicks Seminar Room J11
  Abstract:
Hecke algebras arise in various contexts in Mathematics, ranging from knot theory (construction of the famous Jones polynomial) to the theory of finite groups. They possess a rich and involved combinatorial structure. The purpose of the talk is to explain the role that these algebras play in the representation theory of finite groups and to highlight some recent advances.
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Mar 2 Fri Neil Dummigan (Sheffield) Algebra / Algebraic Geometry seminar
14:10 p-adic Hodge theory II
Hicks Seminar Room J11
  Abstract:
Big rings, comparison theorems, de Rham and crystalline representations.
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Mar 5 Mon Jos (Universidad Nacional Aut) Topology Seminar
14:00 Characteristic Classes and Transversality
Hicks Seminar Room J11
  Abstract:
Let $\xi$ be a smooth vector bundle over a differentiable manifold $M$. Let $h : \epsilon^{n-i+1}\to \xi$ be a generic bundle morphism from the trivial bundle of rank $n-i+1$ to $\xi$. We give a geometric construction of the Stiefel-Whitney classes when $\xi$ is a real vector bundle, and of the Chern classes when $\xi$ is a complex vector bundle. Using $h$ we define a differentiable closed manifold $Z(h)$ and a map $\phi : Z(h)\to M$ whose image is the singular set of $h$. The $i$-th characteristic class of $\xi$ is the Poincaré dual of the image, under the homomorphism induced in homology by $\phi$, of the fundamental class of the manifold $Z(h)$. We extend this definition for vector bundles over a paracompact space, using that the universal bundle is filtered by smooth vector bundles.
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Mar 6 Tue Martin Crossley (Swansea) Topology Seminar
14:00 Word Hopf Algebras
Hicks Seminar Room J11
  Abstract:
Hopf algebras of words appear in many contexts, particularly in topology and in combinatorics. I'll discuss a few of these situations a number of results both old, new, false and true about them.
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Mar 7 Wed T. Talipova (Institute of Applied Physics, Russian Academy of Sciences) Applied Mathematics Colloquium
16:00 The Gardner equation in nonlinear theory of wave motion in stratified medium
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Mar 7 Wed Elmer Rees (Bristol) Pure Maths Colloquium
16:15 Frobenius's higher characters and some more recent developments
Hicks Seminar Room J11
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Mar 9 Fri Neil Dummigan (Sheffield) Algebra / Algebraic Geometry seminar
14:10 p-adic Hodge theory III
Hicks Seminar Room J11
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Mar 13 Tue Richard Hepworth (Sheffield) Topology Seminar
14:00 Chen-Ruan Cohomology
Hicks Seminar Room J11
  Abstract:
Chen-Ruan cohomology seems to be the correct notion of cohomology for orbifolds. Sadly, the definition is rather complicated since it involves differential operators on Riemann surfaces. I will motivate and define orbifolds and Chen-Ruan cohomology before explaining how all of the complications can be reduced to a single property of the so-called age grading.
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Mar 14 Wed Andrew Booker (Bristol) Pure Maths Colloquium
16:00 New twists on an old idea of Turing
Hicks Seminar Room J11
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Mar 16 Fri Frazer Jarvis (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Introduction to group schemes
Hicks Seminar Room J11
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Mar 20 Tue Julia Singer (Bonn) Topology Seminar
14:00 Equivariant Lambda Rings
Hicks Seminar Room J11
  Abstract:
The existence of commutative multiplications on Moore spectra for certain types of rings leads to algebraic conditions providing additional structure on the rings. I'll explain why this can be thought of as an equivariant generalisation of a lambda ring structure.
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Mar 21 Wed May-Win Thein (New Hampshire) Applied Mathematics Colloquium
16:00 Celestial Navigation (CelNav): Lunar Surface Navigation
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Mar 21 Wed Harold Stark (California, San Diego) Pure Maths Colloquium
16:15 The Gauss Class-Number Problems
Hicks Seminar Room J11
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Mar 22 Thu Panagiotis Tsaknias (Sheffield) Pure Maths Postgraduate Seminar
12:10 "Constructing Galois representations from modular forms"
Hicks Seminar Room J11
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Mar 22 Thu Søren Asmussen (Aarhus) Statistics Seminar
14:00 Tail Probabilities for a Computer Reliability Problem
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Mar 23 Fri Frazer Jarvis (Sheffield) Algebra / Algebraic Geometry seminar
14:10 To be announced
Hicks Seminar Room J11
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Apr 18 Wed Jonathan Pila (Bristol) Pure Maths Colloquium
16:00 Density of rational points
Hicks Seminar Room J11
  Abstract:
The basic questions of diophantine geometry concern rational or integral points on an algebraic variety: do they exist, how can they be described (or found), how are they distributed, etc. Such questions lead to deep theorems (often ineffective in various ways) and far-reaching conjectures. This talk will be about a circle of problems and results on giving simply upper bound estimates for the number of integer or rational points up to a given height. I will describe a quite elementary method that yields results that, while relatively weak for an individual variety, are uniform over large classes of varieties. This uniformity has made the results useful. The same methods are also applicable to certain nonalgebraic sets. I will describe a result about rational points on the graph of a transcendental real-analytic function and a connection with transcendence theory. I will finally describe a result on the rational points of analytic (and more general) sets of arbitrary dimension and further connections with transcendence theory.
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Apr 18 Wed Patrick Fowler (Sheffield (Chemistry Department)) Applied Mathematics Colloquium
16:00 Mapping currents in molecules
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Apr 25 Wed Christian Boehmer (Portsmouth) Applied Mathematics Colloquium
16:00 Does the cosmological constant imply the existence of a minimal energy density?
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Apr 27 Fri Jayanta Manoharmayum (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Deformations of Galois representations
Hicks Seminar Room J11
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Apr 30 Mon Constanze Roitzheim (Sheffield) Chromatic homotopy
13:00 Hopf Invariant One for Odd Primes
Hicks Seminar Room J11
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May 2 Wed Tom Van Doorsselaere (Warwick) Applied Mathematics Colloquium
15:00 Recent results in coronal loop seismology: determination of the non-ideal damping mechanism and the density scale height
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May 2 Wed Simon Wadsley (Cambridge) Pure Maths Colloquium
16:00 $K_0$ of p-torsion modules for Iwasawa algebras
Hicks Seminar Room J11
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May 3 Thu Harry Ullman (Sheffield) Pure Maths Postgraduate Seminar
12:10 The Stable Splitting of $U(n)$
Hicks Seminar Room J11
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May 3 Thu Chris Williams (Edinburgh) Statistics Seminar
14:00 Gaussian processes and machine learning
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May 4 Fri Jayanta Manoharmayum (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Deformations of Galois representations II
Hicks Seminar Room J11
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May 8 Tue Ruben Sanchez (Sheffield) Topology Seminar
14:00 Computing Borel's regulator
Hicks Seminar Room J11
  Abstract:
The Borel's regulator map is a useful tool to study the higher algebraic K-theory of the ring of integers of an algebraic number field. In 2000, Hamida proved a formula for the Borel's regulator as an integral of non-commutative differential forms. We will present a formula to approximate this integral which can lead to explicit computations. Finally, we will discuss a p-adic version of this.
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May 9 Wed Jerome Scherer (UAB Barcelona) Pure Maths Colloquium
16:00
Hicks Seminar Room J11
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May 9 Wed Sergei Nazarenko (Warwick) Applied Mathematics Colloquium
16:00 Leith-type model of 2D turbulence and its predictions
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May 10 Thu Simon Tavaré (Southern California) Statistics Seminar
14:00 Stochastic processes in stem cell evolution
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May 11 Fri Cristina Lopez Martin (University of Salamanca (visiting Warwick)) Algebra / Algebraic Geometry seminar
14:10 Fourier-Mukai transforms and moduli spaces of sheaves on elliptic curves
Hicks Seminar Room J11
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May 15 Tue Richard Hepworth (Sheffield) Topology Seminar
14:00 What is a KO object?
Hicks Seminar Room J11
  Abstract:
The real question is "What is an elliptic object?". Stolz and Teichner have been trying to answer this, and along the way they have developed a new perspective on K-theory. In this expository talk I'll try to explain a little bit of this, hopefully ending with a sketch of Stolz-Teichner's theorem describing the KO-theory spectrum in terms of euclidean field theories.
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May 16 Wed Jacek Brodzki (Southampton) Pure Maths Colloquium
16:00 Why can't metric spaces be more like groups?
Lecture Theatre 2
  Abstract:
Research into the Baum-Connes conjecture and related issues provides examples of non-trivial and fruitful interactions between analysis and geometry of (among others) discrete groups. On the other hand, ideas of Gromov, Roe and others gave rise to a programme of large- scale geometry, where two objects are declared equivalent if they "look the same" from a distance. In this talk I shall describe new ideas and results that arise from efforts to unify certain features of both programmes.
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May 16 Wed Roddy Vann (York) Applied Mathematics Colloquium
16:00 A burning fusion plasma: theoretical challenges
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May 18 Fri Helena Fischbacher-Weitz (University of Southampton) Algebra / Algebraic Geometry seminar
14:10 An equivariant Riemann-Roch theorem for curves
Hicks Seminar Room J11
  Abstract:
Let $X$ be an algebraic curve over a field $k$, let $D$ be a divisor on $X$, and let $\mathcal{O}_X(D)$ denote the invertible sheaf (or line bundle) associated to D on X. We are interested in the 0-th cohomology group $H^0(X,\mathcal{O}_X(D))$ of this sheaf, which can be viewed a space of functions on X whose pole and zero orders are bounded by the values of D. Its dimension as a k-vector space is computed by the ``classical'' Riemann-Roch theorem: $$ \dim H^0(X, \mathcal{O}_X(D)) - \dim H^1(X, L(D))= deg D + 1 - g,$$ where $g$ is the genus of $X$. If we now consider the action of a finite group $G$ on $X$, and if we require $D$ to be $G$-stable, then $G$ also acts on the cohomology groups of $\mathcal{O}_X(D)$, and we have Riemann-Roch type theorems which compute the equivariant Euler characteristic $$ [H^0(X, \mathcal{O}_X(D))] - [H^1(X,\mathcal{O}_X(D))]$$ as an element of the Grothendieck group of $k[G]$-modules, and further in the Grothendieck group of projective $k[G]$-modules. The emphasis in this talk will be on the case where the underlying field $k$ is perfect, but not necessarily algebraically closed.
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May 21 Mon Tore Kro (NTNU) Topology Seminar
14:00 Geometry of elliptic cohomology
Hicks Seminar Room J11
  Abstract:
We review what elliptic cohomology is. Furthermore, we will mention the various attempts to define it geometrically. In the program initiated by Baas, the idea is to consider 2-vector bundles. We will look at their definition, and the related notion of charted 2-bundles, and give examples.
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May 22 Tue Tore Kro (NTNU) Topology Seminar
14:00 What does the nerve of a 2-category classify?
Hicks Seminar Room J11
  Abstract:
We outline the proof showing that the nerve of a topological 2-category classifies charted 2-bundles structured by this 2-category. As a corollary, we will see that the K-theory associated to Baez and Crans 2-vector bundles splits as two copies of ordinary K-theory.
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May 22 Tue Andrei Caldararu (Wisconsin) GATA Seminar
15:45 The Mukai pairing on Hochschild homology
Hicks Seminar Room J11
  Abstract:
Given a Calabi-Yau three-fold X, string theory constructs two so-called topological twists, the A-model and the B-model. A piece of the mathematical incarnation of the A-model is the singular cohomology ring of X (or its quantum deformation). The corresponding piece in the B-model is encoded by the Hochschild cohomology ring of X. Physics predicts both sets of data are Frobenius algebras, i.e., they are endowed with a non-degenerate pairing. In the A-model, this is given by the Poincare pairing on cohomology. In my talk I shall discuss the construction of the corresponding pairing on Hochschild (co)homology. I shall also discuss several important properties of this pairing, including the Cardy condition from open-closed topological string theory.
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May 23 Wed Johan Anderson (Sheffield) Applied Mathematics Colloquium
16:00 Comparison of theoretical models to zonal flow generation and the effects of back-reaction of zonal flows on ITG turbulence
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May 23 Wed Andrei Caldararu (Wisconsin) GATA Seminar
16:00 The Pfaffian-Grassmannian derived equivalence
Hicks Seminar Room J11
  Abstract:
We argue that there exists a derived equivalence between Calabi-Yau threefolds obtained by taking hyperplane sections (of the appropriate codimension) of the Grassmannian G(2,7) and the Pfaffian Pf(7). The existence of such an equivalence has been conjectured by physicists for almost ten years, as the two families of Calabi-Yau threefolds are believed to have the same mirror. It is the first example of a derived equivalence between Calabi-Yau threefolds which are provably non-birational.
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May 25 Fri Jonathan Elmer (University of Kent) Algebra / Algebraic Geometry seminar
14:10 Modular Invariant Rings of Minimal Depth
Hicks Seminar Room J11
  Abstract:
Let G be a finite group, V a kG-module over a field k of characteristic p, and R:=S(V^*), and let R^G be the corresponding ring of invariants. It is well known that if p does not divide |G|, then R^G is a Cohen-Macaulay ring. Equivalently, depth(R^G) = dim(R^G), or "R^G has maximal depth". Little is known in general about the depth of modular invariant rings in general, although thanks to Ellingsrud and Skjelbred we do have a lower bound for depth(R^G). A representation V for which this lower bound is attained is called "flat". In this talk we introduce a slightly narrower class of representations (called "strongly flat") and show that although not all flat representations are strongly flat, this notion is sufficiently general to produce a wealth of new examples of flat representations.
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May 29 Tue Ieke Moerdijk (Sheffield) Topology Seminar
14:00 To what extent is Lie theory for groupoids like that for groups?
Hicks Seminar Room J11
  Abstract:
Lie groupoids play an increasingly important role in foliation theory, symplectic and Poisson geometry, and non-commutative geometry. In this lecture, we explain how some basic properties of Lie groups extend to groupoids, and how some other properties don't. The talk will only presuppose some basic familiarity with Lie groups, and in particular should be understandable to the students who attended my recent RTP course.
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May 30 Wed Ruben Sanchez (Sheffield) Topology Seminar
16:00 Computing Borel's regulator II
Hicks Seminar Room J11
  Abstract:
The Borel's regulator map is a useful tool to study the higher algebraic K-theory of the ring of integers of an algebraic number field. In 2000, Hamida proved a formula for the Borel's regulator as an integral of non-commutative differential forms. We will present a formula to approximate this integral which can lead to explicit computations. Note: This talk is independent of the first one except some knowledge of algebraic K-theory and motivation.
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May 30 Wed Daniel Brown (Aberystwyth) Applied Mathematics Colloquium
16:00 The onset of x-ray bright points in the solar corona
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May 31 Thu Mark Davis (Imperial) Statistics Seminar
14:00
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Jun 6 Wed Shunsuke Takagi (Fukuoka)
13:30 Finiteness properties of rings with finite F-representation type
Hicks Seminar Room J11
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Jun 6 Wed Rodney Sharp (Sheffield)
14:40 Further interactions between graded annihilators and tight closure
Hicks Seminar Room J11
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Jun 6 Wed Reza Tavakol (Queen Mary) Applied Mathematics Colloquium
16:00 Dynamo models and differential rotation in the Sun and late-type rapidly rotating stars
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Jun 6 Wed Craig Huneke (University of Kansas) GATA Seminar
16:00 How many times does a polynomial vanish at a point? (GATA lecture I)
Hicks Seminar Room J11
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Jun 7 Thu Shunsuke Takagi (Fukuoka)
11:00 Rationality of F-jumping exponents on singular varieties
Hicks Seminar Room J11
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Jun 7 Thu Yuji Yoshino (Okayama)
13:30 Non-commutative parameter algebras of universal liftings of chain complexes
Hicks Seminar Room J11
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Jun 7 Thu Holger Brenner (Sheffield)
14:40 Some challenging examples for the localization problem in tight closure
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Jun 7 Thu Craig Huneke (University of Kansas) GATA Seminar
16:00 Reduction to characteristic p, and further refinements of vanishing along algebraic subsets (GATA lecture II)
Hicks Seminar Room J11
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Jun 8 Fri Vladimir Bavula (Sheffield)
11:00 The Jacobian map, the Jacobian group and the group of automorphisms of the Grassmann algebra
Hicks Seminar Room J11
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Jun 8 Fri Yuji Yoshino (Okayama)
13:30 Local cohomologies with non-closed supports
Hicks Seminar Room J11
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Jun 8 Fri Moty Katzman (Sheffield)
14:40 Frobenius structures on injective hulls and their applications
Hicks Seminar Room J11
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Jun 8 Fri Craig Huneke (University of Kansas) GATA Seminar
16:00 Absolute integral closures in mixed characteristic and characteristic p (GATA lecture III)
Hicks Seminar Room J11
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Sep 25 Tue Birgit Richter (Hamburg)
16:00 K-theory of 2-vector spaces
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Sep 26 Wed Birgit Richter (Hamburg)
14:00 K-theory of bipermutative categories I
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Sep 27 Thu Birgit Richter (Hamburg)
14:00 K-theory of bipermutative categories II
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Oct 2 Tue Eugenia Cheng (Sheffield) Topology Seminar
14:00 An operadic approach to $n$-categories
Hicks Seminar Room J11
  Abstract:
Operads provide a way of studying loop spaces, by giving a formalism for keeping track of weakly associative multiplication. In this talk I will discuss how this is related to study of weak $n$-categories, where now we must keep track of weakly associative composition. I will present the definition of weak $n$-category proposed by Trimble, which uses one specific and very straightforward topological operad. This can be generalised so that we can use other operads such as the little intervals operad and possibly many of your favourite loop space operads.
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Oct 3 Wed Vic Snaith (Sheffield) Pure Maths Colloquium
16:30 From Algebraic Cobordism to Algebraic Cobordism in only 31 Years
Hicks Seminar Room J11
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Oct 4 Thu Kirill Mackenzie (Sheffield)
12:10 Lie algebras: integration by paths
Hicks Seminar Room J11
  Abstract:
There are several distinct proofs of the integrability of (finite dimensional, real) Lie algebras, but the main purpose of this seminar is to describe the proof of Duistermaat using path spaces. This method is the foundation of the solution of the integrability problem for Lie algebroids and in retrospect can also be seen as underlying the construction by Cattaneo and Felder of a symplectic realization for any Poisson manifold, using Poisson sigma models. If time and interest are available there will be a second talk on (Poisson) sigma models which I hope will provide some background for Cattaneo's talk in Sheffield on October 24th.
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Oct 5 Fri David Gepner (Sheffield) Higher Category Theory
13:00 Organisational meeting
Hicks Lecture Room 10
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Oct 5 Fri Mykola Gordovskyy (Sheffield)
13:05
Lecture Theatre 9
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Oct 9 Tue Paul Mitchener (Sheffield) Topology Seminar
14:00 Coarse Geometry
Hicks Seminar Room J11
  Abstract:
Topology arises from the study of continuous maps, and essentially what happens at very small distances. Coarse geometry, by contrast, ignores all local structure, and only examines very large scale details. Essentially, all that matters in coarse geometry is what is going on `at infinity'. In this talk we will introduce the basic notions of coarse geometry, along with a number of examples and coarse invariants that are analogous to standard invariants in algebraic topology.
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Oct 9 Tue David Applebaum (Sheffield)
17:00 Some Random Thoughts on the Laplacian
Hicks Lecture Theatre 7
  Abstract:
The Laplacian is one of the most important linear operators in mathematics. One reason for this is its ubiquitous role in important second order partial differential equations (pdes) and this lecture will focus mainly on the heat equation. I'll describe the probabilistic method of solving this pde using Brownian motion and show how this relates to the modern analytical approach via semigroup theory. In the last part of the talk, we'll bring in some geometry and I'll describe how the Laplacian on a compact Riemannian manifold can yield information about the curvature.
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Oct 10 Wed Tim Dokchitser (Cambridge) Pure Maths Colloquium
16:00 Parity Conjecture for elliptic curves
Hicks Seminar Room J11
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Oct 10 Wed Dr Matthew P.Juniper (University of Cambridge) Applied Mathematics Colloquium
16:00 'Absolute Stability in Fuel Injectors'
Hicks Lecture Theatre 6
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Oct 11 Thu Richard Jacques (University of Sheffield) Statistics Seminar
14:00 Classification Methods for the Analysis of High Content Screening Data
Hicks Room K14
  Abstract:
The current paradigm for the identification of candidate drugs within the pharmaceutical industry typically involves the use of high throughput screens. A high throughput screen allows a large number of compounds to be tested in a biological assay in order to identify any activity inhibiting or activating a biological process. From each of the assays run through a high throughput screen a high content screen image is produced which can be analysed using advanced imaging algorithms to produce a set of variables which reflect the observed activity of the cells within the image. Classification methods have important applications in the analysis of high content screening data where they are used to predict which compounds have the potential to be developed into new drugs. Statistical approaches have been developed that enable classification using a single parameter. However, approaches for multi-parametric selection are still in their infancy. Furthermore, proper exploitation of the information contained within each high content screen image will enable more refined compound selection. A new classification technique for the analysis of data from high content screening experiments will be presented and the methodology illustrated on an example data set using a random forest classifier.
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Oct 11 Thu Michailina Siakalli (University of Sheffield) Statistics Seminar
14:00 Stochastic Stabilization
Hicks Room K14
  Abstract:
In simple words stability of a dynamic system means sensitivity of the system to changes. Consider a first order non-linear differential equation system dx(t)\dt=f(x(t)). Investigating what happens when noise is added, it has so far been observed that Brownian motion noise can stabilize an unstable system or destabilize it in the case that is stable. In my talk I will describe what is happening when the given non-linear system is perturbed by different types of Poisson noise.
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Oct 12 Fri Eugenia Cheng (Sheffield) Higher Category Theory
13:00 Introduction
Hicks Seminar Room J11
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Oct 12 Fri Johan Anderson (Sheffield)
13:05
Lecture Theatre 9
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Oct 12 Fri Simon Willerton (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Low-dimensional algebra
Hicks Seminar Room J11
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Oct 15 Mon Kirill Mackenzie (Sheffield)
14:30 Integration of Lie algebras, continued
Hicks Seminar Room J11
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Oct 16 Tue Teimuraz Pirashvili (Leicester) Topology Seminar
14:00 Second Hochschild cohomology and triangulated categories
Hicks Seminar Room J11
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Oct 17 Wed David Rydh (Stockholm) Algebra / Algebraic Geometry seminar
13:10 Submersions and effective descent of etale morphisms
Hicks Seminar Room J11
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Oct 17 Wed Elizabeth Allman (Fairbanks, visiting Newton institute) Pure Maths Colloquium
16:00 Models of DNA site substitution
Hicks Seminar Room J11
  Abstract:
Molecular phylogenetics is concerned with inferring evolutionary relationships (phylogenetic trees) from biological sequences (such as aligned DNA sequences for a gene shared by a collection of species). The probabilistic models of sequence evolution that underly statistical approaches in this field exhibit a rich algebraic structure. After an introduction to the inference problem and phylogenetic models, this talk will survey some of the highlights of current algebraic understanding. Results on the important statistical issue of identifiability of phylogenetic models will be emphasized, as the algebraic viewpoint has been crucial to obtaining such results.
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Oct 18 Thu Steve Buckland (The National Centre for Statistical Ecology) RSS Seminar
14:30 Embedding population dynamics models in inference
Hicks Room K14
  Abstract:
Increasing pressures on the environment are generating an ever-increasing need to manage animal and plant populations sustainably, and to protect and rebuild endangered populations. Effective management requires reliable mathematical models, so that the consequences of management action can be predicted, and the uncertainty in these predictions quantified. These models must be able to predict the response of populations to anthropogenic change, while handling the major sources of uncertainty. We describe a simple Â'building blockÂ' approach to formulating discrete-time models. These models may include demographic stochasticity, environmental variability through covariates or random effects, multi-species dynamics such as in predator-prey and competition models, movement such as in metapopulation models, non-linear effects such as density dependence, and mating models. We discuss methods for fitting such models to time series of data, and quantifying uncertainty in parameter estimates and population states, including model uncertainty, using computer-intensive Bayesian methods.
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Oct 18 Thu Rachel Borysiewicz (The National Centre for Statistical Ecology) RSS Seminar
14:30 Integrated population modelling for multi-site data
Hicks Room K14
  Abstract:
The statistical analysis of mark-recapture-recovery (MRR) data collected on wild animal populations dates back to the 1960s, when the foundation was laid for stochastic models fitted to data by the method of maximum likelihood. In recent years an active area of research has developed which combines MRR data with census data. The census data can be described by state-space models and the Kalman filter provides a mechanism for forming the census likelihood. Model fitting then follows by maximising a combined likelihood that is the product of component likelihoods. By combining multiple data sources it has been found that as well as increasing precision of common parameters, it is also possible to estimate parameters which would be inestimable from the analysis of the separate data alone. This methodology is termed integrated population modelling. A particular focus of this talk will be to discuss integrated population modelling for multi-site data, which arises when animals live in and move between different locations. By making use of movement information provided by MRR data, it is possible to avoid flat likelihood surfaces, thus allowing the estimation of site-dependent parameters. The benefits of performing integrated population modelling on multi-site data will be highlighted through both simulated and real data applications.
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Oct 18 Thu Toby Reynolds (The National Centre for Statistical Ecology) RSS Seminar
14:30 Integrated data analysis in the presence of emigration and tag loss: A study of common guillemots on (and off) the Isle of May
Hicks Room K14
  Abstract:
In recent years, many UK seabird populations have experienced dramatic breeding failures and lower than average survival. The common guillemot (Uria aalge) is among those species to suffer. The causes of these events are likely due to a combination of over-fishing and environmental change affecting their primary prey species, the lesser sandeel (Ammodytes marinus). We need to understand the dynamics of seabird populations, in order to determine the implications of future breeding failures and enable us to monitor or predict the effects of future changes in the marine environment. Integrated population modelling provides a useful and robust means to achieve this. An integrated analysis will be presented of four long-term datasets relating to a single guillemot colony on the Isle of May, southeast Scotland (a population of about 20,000 breeding pairs). These comprise abundance, MRR (two datasets) and productivity data. A particular complication with guillemot population dynamics arises due to unobservable emigration of immature birds. In traditional analyses using only MRR data, emigration is confounded with tag loss in the estimation of `fidelity' probabilities, and it is only possible to estimate their product. By combining all available data for the Isle of May guillemots, we are able to provide separate estimates for emigration and tag loss. This model provides a framework which may be used for prediction under various future scenarios.
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Oct 19 Fri Urmila Mitra-Kraev (Sheffield)
13:05
Lecture Theatre 9
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Oct 22 Mon Paul Mitchener (Sheffield) Non-commutative Geometry, Analysis and Groups
17:00 Motivation and Introduction to the Index Theorem
Hicks Seminar Room J11
  Abstract:
We will look at de Rham cohomology, the Euler characteristic, differential operators, and the Gauss-Bonnet formula in an attempt to motivate the Atiyah-Singer index theorem before stating the theorem in its general form. The plan is for this to be a short talk; we will work out organisational details for the rest of the semester afterwards.
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Oct 26 Fri Sergei Zharkov (Sheffield)
13:05
Lecture Theatre 9
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Oct 26 Fri Almar Kaid (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Frobenius descent for vector bundles
Hicks Seminar Room J11
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Oct 29 Mon Bruce Bartlett Higher Category Theory
16:00 Degenerate Higher Categories II
Hicks Seminar Room J11
  Abstract:
This is part II of the talk from last week. I will recap the idea of the periodic table and what the stabilization hypothesis is about. Then we'll relate the ideas of suspension, looping, and stabilization in higher categories to the corresponding ideas in topology. Finally we'll look at the "second column" of the periodic table, explaining the kinds of algebraic structures which appear there - with plenty of examples (*) - and also explain how suspension and looping work on these structures. (*) One of the algebraic structures appearing in the second column of the periodic table is a "braided monoidal category". I will try to mention the idea due to Grothendieck and Drinfeld, once explained to me by Frazer, that the "group of deformations" of a certain natural braided monoidal category is somehow isomorphic to the absolute Galois group from number theory.
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Oct 29 Mon John Greenlees (Sheffield) Non-commutative Geometry, Analysis and Groups
17:00 Characteristic Classes
Hicks Seminar Room J11
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Oct 30 Tue Shoham Shamir (Sheffield) Topology Seminar
14:00 Cellular approximations and the Eilenberg-Moore spectral sequence
Hicks Seminar Room J11
  Abstract:
Given chain-complexes k and M over a ring R, a k-cellular approximation to M is the "closest approximation" of M that can be glued together from copies of suspensions of k. I will discuss this concept (due to Dwyer, Greenlees and Iyengar) and how is can be used to study the Eilenberg-Moore cohomology spectral sequence for a fibration.
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Oct 31 Wed Wilhelm Klingenberg (Durham) Pure Maths Colloquium
16:00 Fibrations by geodesics, spacelike surfaces, and the standard tight contact structure
Hicks Seminar Room J11
  Abstract:
A regular fibration by geodesics of a three-dimensional space form is represented by a spacelike surface in four-dimensional moduli space of geodesics. In the euclidean case, the standard contact structure is perpendicular to such a fibration. Solemn undertaking: "I would make it accessible to any math grad student..."
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Oct 31 Wed Professor Alan Zinober (Sheffield) Applied Mathematics Colloquium
16:00 'Optimal Control and Some Applications in Operations Research'
Hicks Lecture Theatre 6
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Nov 2 Fri Gemma Attrill (MSSL)
13:05
Lecture Theatre 9
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Nov 2 Fri Barrie Cooper (Sheffield) Algebra / Algebraic Geometry seminar
14:10 Almost Koszul algebras and rational conformal field theory I
Hicks Seminar Room J11
  Abstract:
The preprojective algebra of a non-Dynkin graph is Koszul and can be identified with the functorial image of a Koszul ``universal preprojective algebra object'' in the Temperley-Lieb category. This line of thought also helps identify what happens to make the Dynkin preprojective algebras ``almost Koszul'' and elicits interesting connections to conformal field theory and quantum subgroups of sl(2). In the second talk I will discuss the sl(3) case and use these connections to construct new examples of almost Koszul algebras. The talk will be pretty basic, with the aim of rendering the abstract comprehensible to a graduate student.
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Nov 5 Mon Richard Hepworth (Sheffield) Non-commutative Geometry, Analysis and Groups
17:00 Dirac Operators
Hicks Seminar Room J11
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Nov 6 Tue James Cranch (Sheffield) Topology Seminar
14:00 Spannish for beginners
Hicks Seminar Room J11
  Abstract:
I will say something about the notion of a span category, the appropriate analogue in the language of quasicategories, and what all this is supposed to have to do with homotopy theory.
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Nov 7 Wed Bob Coecke (Oxford) Pure Maths Colloquium
16:00 Kindergarten Quantum Mechanics
Hicks Seminar Room J11
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Nov 7 Wed Dr C.J.Howls (Southampton) Applied Mathematics Colloquium
16:00 'Why is a Shock Not a Caustic?
Hicks Lecture Theatre 6
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Nov 8 Thu Markus Riedle (University of Manchester) Statistics Seminar
14:00 Introduction to stochastic delay differential equations
Hicks Room K14
  Abstract:
In the last years stochastic functional differential equations or stochastic differential equations with delay have gained increasing attention in several scientific areas such as economy, biology, physics and medicine. The reason can be found in the observation that in a huge variety of models the evolution of the process describing the dynamics in the model under consideration not only depends on the current state of the process but also on its former states. This effect is due to various reasons such as time to maturity, incubation time, time to build, time to transport, hysteresis, delayed feedback and past dependent volatility. In the beginning of the talk we present some of these applications of stochastic functional differential equations. We introduce the basic ideas of ordinary stochastic differential equations not depending on the past and explain how these equations can be generalised to functional equations covering the examples presented before. The fundamental theory of stochastic functional differential equations are introduced and in particular compared with the situation of ordinary stochastic differential equations. In the remaining part of the talk we distinguish several cases how the random noise and past dependence enter the equation and we focus here on asymptotic aspects of the solution. We present some phenomena only known from delay equations. We also introduce some results which explain the relation of functional and partial stochastic differential equations.
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Nov 9 Fri Youra Taroyan (Sheffield)
13:05
Lecture Theatre 9