Sep 26  Tue  TBA  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Sep 28  Thu  Muralikrishnan Gopalakrishnan Meena (Oak Ridge National Laboratory)  Plasma Dynamics Group  
16:00  Vortical network connectors for turbulence modification  
https://meet.google.com/piydqagwym  
Abstract: The interactiondriven evolution of complex systems in both natural and engineering contexts offers a unique opportunity to leverage graph theory for understanding their behavior as well as for modeling and modifying their evolution. This seminar aims to introduce a network (graph) communitybased framework to perform flowmodification of turbulent vortical flows. The present framework captures vortical interactions on a network, where the vortical elements are viewed as the nodes and the vortical interactions are regarded as edges weighted by induced velocity from the BiotSavart law. The networkbased community detection algorithm is used to identify a group of closely interacting vortical elements, called communities. The inter and intracommunity interactions are used to identify the communities that have the strongest and weakest interactions amongst them, referred to as the connector and peripheral communities, respectively. For isotropic turbulence, the connector and peripheral communities correspondingly resemble shearlayer and vortexcore like structures. Results show that perturbing the connector structures enhances local turbulent mixing beyond what is achieved by perturbing the strongest vortex tube and shearlayer regions. 



Oct 2  Mon  Andrew Krause (Durham)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Oct 3  Tue  TBA  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Oct 3  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Oct 4  Wed  Tyler Kelly (Birmingham)  Pure Maths Colloquium  
14:00  Moduli of genuszero higher spin curves and their invariants  
Hicks Seminar Room J11  
Abstract: In mathematics, we like classifying objects. A moduli space is a space where each point represents a(n isomorphism class of a) space satisfying certain criteria, giving a geometric answer to a classification problem. Often the geometry of such spaces are interesting in our own right and their corresponding enumerative information has rich structure. We will study the case of genuszero npointed curves and a generalisation where they are further equipped with an rspin structure. Enumerative invariants built from their characteristic classes have rich structure due to generalisations of predictions of Witten confirmed by Kontsevich. We will explain approaches to understanding these invariants on a very concrete level through combinatorial structures like recursion and tropical geometry. 



Oct 4  Wed  Ilay Hoshen (Tel Aviv)  Probability seminar  
15:00  Simonovits's theorem in random graphs  
Hicks Seminar Room J11  
Abstract: Let $H$ be a graph with chromatic number $\chi(H) = r+1$. Simonovits's theorem states that the unique largest $H$free subgraph of $K_n$ is its largest $r$partite subgraph if and only if $H$ is edgecritical. We show that the same holds with $K_n$ replaced by $G_{n,p}$ whenever $H$ is also strictly 2balanced and \begin{align*} p \geq C n^{1/m_2(H)} \log(n)^{1/(e(H)1)}, \end{align*} for some constant $C > 0$. This is best possible up to the choice of the constant $C$. This (partially) resolves a conjecture of DeMarco and Kahn, who proved the result in the case where $H$ is a complete graph. Moreover, we prove the result with explicit constant $C = C(H)$ that we believe to be optimal. Joint work with Wojciech Samotij. 



Oct 4  Wed  Mariaveronica De Angelis (Sheffield)  Cosmology, Relativity and Gravitation  
16:00  Multifield inflation with kinetic couplings: theoretical predictions and observational constraints  
Hicks Seminar Room J11  
Abstract: In the twofield inflationary paradigm, it is commonly assumed that the kinetic coupling between the fields, resulting from a nonminimal coupling in the Jordan frame and leading to a curved field manifold in the Einstein frame, depends solely on one field. Our study delves into the situation where the kinetic coupling can instead vary with both fields. The aim of this study is to investigate adiabatic and isocurvature perturbations within these extended theories. Our analysis reveals that, while the evolution equation for the curvature perturbation remains unchanged when allowing coupling dependence on both fields, the effective mass of the entropy perturbation undergoes modifications. We analytically study the correlations between the models’ free parameters and present also a novel numerical method tailored to the study of general multifield models. Our algorithm captures the dynamics of the fields throughout the entire inflationary phase, providing accurate predictions for observables such as the spectrum of primordial scalar perturbations, primordial gravitational waves, isocurvature modes, and the transfer of entropy to scalar modes after the horizon crossing. By sampling over the initial conditions of the fields and the free parameters of the model, we enable a Monte Carlo analysis, testing the theoretical predictions against observational data. 



Oct 5  Thu  Tyler Kelly (Birmingham)  
11:00  Open FJRW theory and mirror symmetry  
Hicks Seminar Room J11  
Abstract: FJRW theory is an enumerative theory built from characteristic classes corresponding to the moduli space of Wspin curves, a natural generalisation of higher spin curves. They can be interpreted as the enumerative geometry of gauged LandauGinzburg models. We construct an enumerative theory for an open version of FJRW invariants, over the moduli space of Wspin discs, rather than compact Riemann surfaces. We then will build the mirror to the original LandauGinzburg model as a generating function of open FJRW invariants, and prove a mirror symmetry statement. This is joint work with Mark Gross and Ran Tessler. 



Oct 9  Mon  Raj Hossein (Sheffield)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Oct 10  Tue  JuFeng Wu (University of Warwick)  Number Theory seminar  
13:00  On $p$adic adjoint $L$functions for Bianchi cuspforms: the $p$split case  
Hicks Seminar Room J11 / Google Meet  
Abstract: In the late '90's, Coleman and Mazur showed that finiteslope eigenforms can be patched into a rigid analytic curve, the socalled eigencurve. The geometry of the eigencurve encodes interesting arithmetic information. For example, the Bellaïche—Kim method showed that there is a strong relationship between the ramification locus of the (cuspidal) eigencurve over the weight space and the adjoint $L$value. In this talk, based on joint work with PakHin Lee, I will discuss a generalisation of the Bellaïche—Kim method to the Bianchi setting. If time permits, I will discuss an interesting question derived from these $p$adic adjoint $L$functions. 



Oct 10  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Oct 11  Wed  Markus Szymik (Sheffield)  Pure Maths Colloquium  
14:00  
Hicks Seminar Room J11  


Oct 11  Wed  Marco de Cesare (Naples)  Cosmology, Relativity and Gravitation  
15:00  Interacting dark sector from the tracefree Einstein equations: cosmological perturbations with no instability  
Hicks Seminar Room J11  
Abstract: In tracefree Einstein gravity, the energymomentum tensor of matter is not necessarily conserved and so the theory offers a natural framework for interacting dark energy models where dark energy has a constant equation of state w=1. From the point of view of quantum gravity phenomenology, it has been argued that such violations of energymomentum conservation might originate from discreteness at the Planck scale. We show that within this framework it is possible to build models where cosmological perturbations are free from instabilities, which are known to affect a large class of interacting dark energy models. We will also comment on the possibility that the models here considered may help alleviate the Hubble tension. 



Oct 12  Thu  Daniel Graves (Leeds)  Topology Seminar  
16:00  Homology of generalized rookBrauer algebras  
Hicks Seminar Room J11  
Abstract: I will expand on the slogans I gave in last week's gong show. I'll give definitions of some generalizations of rookBrauer algebras (and their subalgebras) by introducing equivariance and braiding. I'll discuss how we can identify the homology of some of these algebras with the group homology of braid groups and certain semidirect product groups. I'll also discuss how we can deduce homological stability results and discuss some ideas for future work. 



Oct 13  Fri  Piyali Chatterjee (IIA)  SP2RC/ESPOS seminar  
13:00  Why do spicules spin in the images taken at the solar limb  
Google meet link: https://meet.google.com/ciqzovurzm  
Abstract: Bunches of swaying spicules in the solar chromosphere exhibit a variety of complex dynamics that are clearly observed in the images of coronal hole regions. By calculating the lineofsight integrated emission from threedimensional radiative magnetohydrodynamic simulations, we obtain multiple episodes of rotation amongst clusters of spicules also reported in the sequence of high cadence observations on the solar limb. This perception of rotation, according to our findings, is associated with hot swirling plasma columns that we label as coronal swirling conduits (CoSCo). Some tall CoSCos seen in our simulations can potentially form by feeding on spicules and channeling this energy to the upper reaches of the solar atmosphere, even while the corresponding spicules fall back sunward. 



Oct 13  Fri  Maria Giovanna Dainotti (National Astronomical Observatory of Japan)  Cosmology, Relativity and Gravitation  
15:00  On the Hubble constant tension  
Hicks Seminar Room J11  
Abstract: The difference from 4$\sigma$ to 6$\sigma$ in the Hubble constant ($H_0$) between the values observed with the local probes (Cepheids and Supernovae Ia, SNe Ia) and the probes at highz (Cosmic Microwave Background obtained by the Planck data) still challenges the astrophysics and cosmology community. Here, we investigate this tension obtained by using the SNe Ia gathered in the Pantheon sample and the Baryon Acoustic Oscillations, assuming $H_0=73.5 $ and $H_0=70 $ as the local value, and dividing the Pantheon sample in 3, 4, and 10 bins ordered in redshift.} For each bin, we run a Monte Carlo MarkovChain (MCMC) analysis obtaining the value of $H_0$. Subsequently, the values of $H_0$ are fitted with the model $g(z)=\tilde{H_0}/(1+z)^\alpha$, where $\tilde{H_0}$ is $H_0(z=0)$ and $\alpha$ is the evolutionary parameter. Our results show that a decreasing trend with $\alpha\sim10^{2}$ is still visible in this sample.} The $\alpha$ coefficient is compatible with zero between 1.1$\sigma$ and 2.2$\sigma$. This trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models such as the $f(R)$ theories of gravity. Assuming a specific $f(R)$ model in the Jordan frame, we find that the results of our analysis remain unchanged. We conclude that this specific model is not appropriate for explaining the effect of the decreasing $H_0$. Furthermore, our analysis gives suggestions on how a cosmological model can be tested taking into account a parametrized evolution of the Hubble constant. A new analysis with SNe Ia, BAO, quasars and GRBs has been performed with new likelihood showing a less pronounced tension with the SNe Ia. 



Oct 16  Mon  TBA  The Sheffield Geometry and Physics Seminar  
10:00  
Hicks Seminar Room J11  


Oct 16  Mon  TBA  The Sheffield Geometry and Physics Seminar  
11:30  
Hicks Seminar Room J11  


Oct 16  Mon  Alex Best (Journal Club) (Sheffield)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Oct 17  Tue  TBA  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Oct 17  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Oct 18  Wed  Lassina Dembele (King's College London)  Black History Month Colloquium  
14:00  How mentorship could help fight underrepresentation in STEM.  
LT5  
Abstract: There is no denial that certain visible minorities are severely underrepresented in STEM. I hear people often say that the best way to fight underrepresentation is to have more role models from those minority groups. That is true, perhaps. However, I believe that there needs to be an intermediate solution until we reach that point when we have enough role models to have an impact. Based on my own personal experience, I want to explain how an innovative approach to mentorship can help fight underrepresentation. 



Oct 18  Wed  Ruchika (INFN Rome)  Cosmology, Relativity and Gravitation  
15:00  Reconciling JWST and HST with Planck  
Hicks Seminar Room J11  
Abstract: The recent observations from the James Webb Space Telescope have led to a surprising discovery of a significant density of massive galaxies with masses of $M \ge 10^{10.5} M_{\odot}$ at redshifts of approximately $z\sim 10$. This corresponds to a stellar mass density of roughly $\rho_*\sim 10^6 M_{\odot} Mpc^{3}$. Despite making conservative assumptions regarding galaxy formation, this finding may not be compatible with the standard $\Lambda$CDM cosmology that is favored by observations of CMB Anisotropies from the Planck satellite. Parallely, SH0ES 2022 results confirmed more than 5 sigma deviation in determining the value of the Hubble Constant from the local distance ladder (using HST) and inverse distance ladder (utilizing Planck). Assuming both SH0ES and the Planck team are not making any errors, I will try to convince them that we need to look for new physics or new theoretical models to alleviate the discrepancy/cosmological crisis. We propose the GTransition hypothesis, a negative cosmological constant model at low redshifts or Interacting Dark Energy/Early Dark Energy to come to the rescue. But before saying anything concrete, we need to see the similar effects in all cosmological probes. 



Oct 19  Thu  Neil Strickland (Sheffield)  Topology Seminar  
16:00  Double subdivision of relative categories  
Hicks Seminar Room J11  
Abstract: By a relative category we mean a category $\mathcal{C}$ equipped with a class $\text{we}$ of weak equivalences. Given such a thing, one can construct a simplicial set $N\mathcal{C}$, called the relative nerve. (In the case where $\text{we}$ is just the class of identity morphisms, this is just the usual nerve of $\mathcal{C}$.) Under mild conditions on $\mathcal{C}$, one can show that $N\mathcal{C}$ is a quasicategory (as defined by Joyal and studied by Lurie), and that the homotopy category of $N\mathcal{C}$ is the category of fractions $\mathcal{C}[\text{we}^{1}]$. Lennart Meier gave a proof of this, but it depended on quoting a large body of theory related to model categories in the sense of Quillen. I will explain a different approach which instead uses more concrete combinatorial constructions with various specific finite posets. 



Oct 23  Mon  Jack Jennings (Sheffield)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Oct 24  Tue  Neil Strickland (Sheffield)  Astronomical Topology Working Group  
09:00  Introduction to Chromatic Homotopy  
Hicks Seminar Room J11  
Abstract: This will be an introduction to chromatic homotopy theory, aiming to give the background required to understand the statement of the Telescope Conjecture. 



Oct 24  Tue  Havard DammJensen  Number Theory seminar  
13:00  Diagonal Restrictions of Hilbert Eisenstein series  
Hicks Seminar Room J11 / Google Meet  
Abstract: Darmon and Vonk's theory of rigid meromorphic cocycles, or "RM theory", can be thought of as a $p$adic counterpart to the classical CM theory. In particular, values of certain cocycles conjecturally behave similarly to values of the modular $j$function at CM points. Recently, Darmon, Pozzi and Vonk proved special cases of these conjectures using $p$adic deformations of Hilbert Eisenstein series. I will describe some ongoing work extending these results, and how to make their constructions effectively computable. 



Oct 24  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  


Oct 25  Wed  Reem Yassawi (Queen Mary University of London)  Pure Maths Colloquium  
14:00  Automatic sequences in dynamics and number theory  
Hicks Seminar Room J11  
Abstract: An infinite sequence $a = (a_n)_{n\geq 0}$ is $q$automatic if an is a finitestate function of the base$q$ expansion of $n$. This means that there exists a deterministic finite automaton that takes the baseq expansion of $n$ as input and produces the symbol an as output for each $n \in \mathbb{N}$. Automatic sequences appear in diverse fields of mathematics, such as algebra, logic, number theory, and topological dynamics. They have the advantage of lend ing themselves to computation, so that in each area there arise specific problems concerning automatic sequences, and much of the time, constructive solutions. I will give a background of their characterisations in algebra and dynamics, via Furstenberg’s, Cobham’s and Christol’s theorems. I will then talk about joint work with Eric Rowland and Manon Stipulanti, concerning automatic sequences in number theory, and also about joint work with Johannes Kellendonk, concerning automatic sequences in topological dynamics, ending with a topological invariant which seems to defy computation. 



Oct 25  Wed  Syed Naqvi (Jagellonian U, Krakow)  Cosmology, Relativity and Gravitation  
15:00  Chaos and EinsteinRosen gravitational waves  
Blackboard Collaborate  
Abstract: In this study, we examine the EinsteinRosen solution to investigate cylindrical standing gravitational waves. Similar to how standing mechanical waves reveal captivating features such as Chladni patterns and nonlinear Faraday waves, these standing gravitational waves also provide valuable insights into nonlinear aspects of general relativity. Our investigation reveals the existence of chaotic geodesics within the EinsteinRosen spacetime, highlighting their sensitivity to initial conditions. This sensitivity is confirmed through the observation of an underlying fractal structure. We elucidate the source of this chaotic behaviour by examining the homoclinic and heteroclinic network. Furthermore, we attribute the intricate dynamics of test particles in this spacetime to the complex interplay between stable and unstable manifolds around hyperbolic points. 



Oct 26  Thu  Merlin Mendonza (National Central University (Taiwan))  Plasma Dynamics Group  
09:00  Association Between Magnetic Pressure Difference and the Movement of Solar Pores  
https://meet.google.com/cgdxjdqqxx / Google Meet  
Abstract: Solar pores are closely related to the concentration, dissipation, and transportation of solar magnetic flux. Their observable characteristics can provide constraints on models and simulations of magnetic flux emergence and formation. The specific property investigated in this study is their horizontal movement. The aim is to investigate whether the movement is correlated with any observable quantities. Our statistical analysis of 61 compact pores identified from the Spaceweather HMI Active Region Patches (SHARP) from 2011 to 2018 indicates that the direction of movement is often either parallel or antiparallel to the direction of maximum magnetic pressure difference at the opposite sides of the edges of the pores. The correlation coefficients for both the parallel and antiparallel cases are higher than 0.74. Despite the high correlation, our analysis using the transfer entropy indicates no significant causal relationship between the direction of motion and the direction of maximum magnetic pressure difference. 



Oct 26  Thu  Marco Schlichting (Warwick)  Topology Seminar  
16:00  On the relation between Hermitian Ktheory and MilnorWitt Ktheory  
Hicks Seminar Room J11  
Abstract: Hermitian Ktheory of a commutative ring R is the algebraic Ktheory of finitely generated projective Rmodules equipped with a nondegenerate symmetric/symplectic/quadratic form. The algebra generated in degree (1,1) modulo the Steinberg relation in degree (2,2) is called MilnorWitt Ktheory and plays an important role in A1homotopy theory. Multiplicativity of Hermitian Ktheory defines a graded ring homomorphism from MilnorWitt Ktheory to Hermitian Ktheory. We prove a homology stability result for symplectic groups and use this to construct a map from Hermitian Ktheory of a local ring to MilnorWitt Ktheory in degrees 2,3 mod 4. Finally, we compute the composition of the maps from MilnorWitt to Hermitian and back to MilnorWitt Ktheory as multiplication with a particular integral form. 



Oct 27  Fri  Simone Chierichini (UoS)  SP2RC/ESPOS seminar  
13:00  A Bayesian approach to the dragbased modelling of ICMEs  
Google meet link: https://meet.google.com/ciqzovurzm  
Abstract: Coronal Mass Ejections (CMEs) are huge clouds of magnetised plasma expelled from the solar corona that can travel towards the Earth and cause significant space weather effects.The DragBased Model (DBM) describes the propagation of CMEs in an ambient solar wind as analogous to an aerodynamic drag.The dragbased approximation is popular because it is a simple analytical model that depends only on two parameters, the drag parameter $\gamma$ and the solar wind speed $w$. DBM thus allows us to obtain reliable estimates of CME transit time at low computational cost. Previous works proposed a probabilistic version of DBM, the Probabilistic Drag Based Model (PDBM), which enables the evaluation of the uncertainties associated with the predictions. In this work, we infer the "aposteriori" probability distribution functions (PDFs) of the $\gamma$ and $w$ parameters of the DBM by exploiting a wellestablished Bayesian inference technique: the Monte Carlo Markov Chains (MCMC) method. By utilizing this Bayesian method through two different approaches, an ensemble and an individual approach, we obtain specific DBM parameter PDFs for two ensembles of CMEs: those travelling with fast and slow solar wind, respectively. Subsequently, we assess the operational applicability of the model by forecasting the arrival time of CMEs. While the ensemble approach displays notable limitations, the individual approach yields promising results, demonstrating competitive performances compared to the current stateoftheart, with a mean absolute error (MAE) of 9.86 ± 4.07 hours achieved in the bestcase scenario. 



Oct 30  Mon  TBA  The Sheffield Geometry and Physics Seminar  
10:00  
Hicks Seminar Room J11  


Oct 30  Mon  TBA  The Sheffield Geometry and Physics Seminar  
11:30  
Hicks Seminar Room J11  


Oct 30  Mon  TBC  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Oct 31  Tue  Robert Kurinczuk (Sheffield)  Number Theory seminar  
13:00  Blocks for classical padic groups  
Hicks Seminar Room J11  


Oct 31  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Nov 1  Wed  Eli Hawkins (University of York)  Pure Maths Colloquium  
14:00  Quantization of Multiply Connected Manifolds  
Hicks Seminar Room J11  
Abstract: Given a compact Kähler manifold satisfying an integrality condition, the BerezinToeplitz geometric quantization construction produces matrix algebras; these fit together into a fundamental example of strict deformation quantization. The integrality condition can be circumvented by passing to the universal covering space, if the lift of the symplectic form is exact; in this case, the symplectic form determines a 2cocycle of the fundamental group. The key to analyzing this construction is to use Hilbert $C^*$modules, which generalize Hilbert spaces. The resulting algebras are more interesting than matrix algebras and are partially determined by index theorems. The simplest example is the noncommutative torus, and this gives highergenus noncommutative Riemann surfaces as well. 



Nov 2  Thu  Pablo Santamarina Guerrero (Instituto de Astrofísica de Andalucía, Spain)  SP2RC/ESPOS seminar  
10:00  Magnetic structure analysis by applying persistent homology to Hinode and SDO magnetograms  
Zoom link: https://zoom.us/j/165498165 (Meeting ID: 165 498 165)  
Abstract: The ability to encode and simplify all information about the shape and distribution of data has turned Topological Data Analysis (TDA) into one of the most relevant fields in stateoftheart data analysis. Among all the tools of TDA, persistent homology has proven to be one of the most relevant techniques, and has been applied in numerous fields of study, such as biomedicine, chemistry, atomic physics, or image classification. In this work, we study what persistent homology can offer in the analysis of solar magnetograms, with the purpose of providing a new tool that will serve as foundation for further studies of magnetic structures on the solar surface. We propose an approach based on the use of persistence diagrams belonging to various filtrations in order to be able to capture the whole magnetic scene involving a mixture of positive and negative polarities. We have applied the analysis to quiet sun and active regions observations, taken with both Hinode/SOT and SDO/HMI, respectively. Persistent diagrams have proven to be able to encode the spatial structure complexity of the magnetic flux of active regions by identifying the isolated and connected (interacting) structures. Holes or pores are also displayed in persistent diagrams, allowing as well for the identification of interacting structures of opposite polarities in the form of ringlike structures. The overall temporal evolution of active regions, as well as small scale events in quiet sun such as magnetic flux cancellation and emergence are also displayed in persistent diagrams and can be studied by observing the evolution of the diagrams and tracking the relevant features. 



Nov 2  Thu  Alex Corner (Sheffield Hallam)  Topology Seminar  
16:30  Weak Vertical Composition  
Hicks Seminar Room J11  
Abstract: A usual test for a suitable semistrict notion of ncategory is that in its degenerate cases, it produces particular lowerdimensional monoidal structures as predicted by Baez and Dolan's Stabilisation Hypothesis. These structures are of interest in topology in that they produce algebraic homotopy ntypes which are not equivalent to a fully strict notion of ncategory. We are concerned with doublydegenerate tricategories, which should produce a structure equivalent to a braided monoidal category. Gordon, Power, and Street show that in the case of Graycategories, where interchange of 2cells is weak but all other composition is strict, this is certainly the case. Joyal and Kock show further that the weakness, like a bump under a carpet, can be pushed solely into the horizontal units for 2cells, and that this notion also matches braided monoidal categories in the doublydegenerate case. In this talk I will introduce a notion of tricategory in which only the vertical composition of 2cells is weak. These will be identified with categories strictly enriched in the category of bicategories and strict 2functors with cartesian monoidal product, which, although constituting an unusual mix of weakness and strictness allows a very straightforward algebraic characterisation of weak vertical tricategories using the theory of 2monads and 2distributive laws. Thus far only objectlevel correspondences have been considered, but we show that with special consideration given to iconlike higher cells, we can form a 2categorical totality of these degenerate structures, along with their weak maps and transformations, allowing us to give a full comparison with the 2category of braided monoidal categories. 



Nov 6  Mon  Tyler Cassidy (Leeds)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Nov 7  Tue  Neil Strickland (Sheffield)  Astronomical Topology Working Group  
09:00  The Telescope Conjecture as Galois theory of ring spectra  
Hicks Seminar Room J11  
Abstract: Let $X$ be a finite $p$torsion spectrum of type $n$, which means that the Morava $K$theory $K(n)_{*}(X)$ is nontrivial, but $K(m)_*(X)=0$ for $m\lt n$. By work of Devinatz, Hopkins and smith, there is a map $v\:\Sigma^dX\to X$ for some $d\gt 0$ such that $K(n)_{*}(v)$ is an isomorphism, and this is nearly natural in a certain sense. We can thus form the colimit $v^{1}X$ of the sequence $X\to\Sigma^{d}X\to\Sigma^{2d}X\to\dotsb$. The Telescope Conjecture predicts that this should be the same as the Bousfield localisation $L_{K(n)}(X)$. There is a certain spectrum $E$ called Morava $E$theory, with a natural action of a group $G$ called the Morava stabiliser group, with the property that $L_{K(n)}(X)$ is the spectrum $(E\wedge X)^{hG}$ of (homotopy) fixed points of the action (by an argument that is not too hard). There is a sense in which $E\wedge X$ is a Galois extension of $L_{K(n)}(X)$ with Galois group $G$, and various other Galois extensions with smaller Galois groups play an important role in the disproof of TC. I will attempt to explain some of these ideas. 



Nov 7  Tue  Jeff Manning (Imperial College London)  Number Theory seminar  
13:00  The WilesLenstraDiamond numerical criterion over imaginary quadratic fields  
Hicks Seminar Room J11  
Abstract: Wiles' modularity lifting theorem was the central argument in his proof of modularity of (semistable) elliptic curves over Q, and hence of Fermat's Last Theorem. His proof relied on two key components: his "patching" argument (developed in collaboration with Taylor) and his numerical isomorphism criterion. In the time since Wiles' proof, the patching argument has been generalized extensively to prove a wide variety of modularity lifting results. In particular Calegari and Geraghty have found a way to generalize it to prove potential modularity of elliptic curves over imaginary quadratic fields (contingent on some standard conjectures). The numerical criterion on the other hand has proved far more difficult to generalize, although in situations where it can be used it can prove stronger results than what can be proven purely via patching. In this talk I will present joint work with Srikanth Iyengar and Chandrashekhar Khare which proves a generalization of the numerical criterion to the context considered by Calegari and Geraghty (and contingent on the same conjectures). This allows us to prove integral "R=T" theorems at nonminimal levels over imaginary quadratic fields, which are inaccessible by Calegari and Geraghty's method. The results provide new evidence in favor of a torsion analog of the classical Langlands correspondence. 



Nov 7  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Nov 8  Wed  Daniel Graves (University of Leeds)  Pure Maths Colloquium  
14:00  Homology of diagram algebras  
Hicks Seminar Room J11  
Abstract: Diagram algebras, such as the Brauer algebras and TemperleyLieb algebras, have been studied for many years. They appear in wideranging places such as statistical mechanics, knot theory and representation theory. However, the study of the homology of these algebras is a very young field indeed, having emerged over the course of last decade. In this talk I will give an introduction to these diagram algebras, their homology and their connection to group homology and homological stability. Time permitting, I will discuss some recent generalizations of these algebras. 



Nov 9  Thu  Wei Xing (Sheffield)  Statistics Seminar  
14:00  Reliable AI for Engineering  
Hicks Seminar Room J11  
Abstract: Artificial intelligence (AI) has seismically shifted the landscape across multiple domains including scientific computing, manufacturing, and engineering. However, the importance of Reliable AI extends beyond what general AI can offer, particularly in scenarios where the stakes are high. Reliable AI, as the name suggests, emphasizes reliability, robustness, and trustworthiness, crucial for realworld applications where uncertainties and highstakes decisions are the norms. In this talk, I will share our development of reliable AI techniques using Bayesian models and how these methods can be implemented to improve problems in integrated circuit design and some other broader applications in engineering such as digital twins. 



Nov 9  Thu  Cosima Breu (St Andrews)  Plasma Dynamics Group  
16:00  Vortices as energy channels into the solar corona  
https://meet.google.com/resiojhths  
Abstract: From water spiralling into a sink drain to mesmerising giant storms on Jupiter, vortex motions are present throughout the universe on scales from the very small to the very large. Vortex flows have been found in the photosphere, chromosphere, and low corona in observations and simulations. It has been suggested that vortices play an important role in channeling energy and plasma into the corona. We investigate the importance of vortices for coronal heating using highresolution simulations of coronal loops driven selfconsistently by magnetoconvection. We performed 3D resistive MHD simulations with the MURaM code. Studying an isolated coronal loop in a Cartesian geometry allows us to resolve the structure of the loop interior. We find that the energy injected into the loop is generated by internal coherent motions within strong magnetic elements. A significant part of the resulting Poynting flux is channeled through the chromosphere in vortex tubes forming a magnetic connection between the photosphere and corona. Vortices have a complex relationship with the coronal emission, and I will discuss how these structures could potentially be observed in the corona. 



Nov 13  Mon  TBA  The Sheffield Geometry and Physics Seminar  
10:00  
Hicks Seminar Room J11  


Nov 13  Mon  TBA  The Sheffield Geometry and Physics Seminar  
11:30  
Hicks Seminar Room J11  


Nov 13  Mon  Alexandria Volkening (Purdue/Cambridge)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Nov 14  Tue  Dan Graves (Leeds)  Astronomical Topology Working Group  
09:00  Background from stable homotopy theory  
Hicks Seminar Room J11  


Nov 14  Tue  TBA  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Nov 14  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Nov 15  Wed  Emre Özülker (Istanbul Tech U.)  Cosmology, Relativity and Gravitation  
15:00  Dark energy phenomenology, negative dark energy density, and the signswitching $\Lambda$  
Hicks Seminar Room J11  
Abstract: A dark energy density that attained negative values in the past is phenomenologically motivated by the presence of this feature in parametric and nonparametric reconstructions of the cosmological functions based on the observational data, and also by the success of cosmological models that feature such a dark energy density in addressing the observational tensions. I show how a negative dark energy density can alleviate the tensions by focusing on the first peak in the cosmic microwave background power spectrum, and what happens to the equation of state parameter of such a (potentially effective) dark energy source when local energymomentum conservation holds. I also argue a negative energy density is not theoretically problematic but even abundant in theoretical physics when treated as an effective source. In the second half, I focus on a specific dark energy model that features a negative density in the past, namely, the signswitching cosmological constant model. I briefly describe how and why the model was introduced, describe its phenomena, show the latest constraints on its parameters, and discuss its extensions and underlying mechanisms. 



Nov 15  Wed  Lukas Lüchtrath (Weierstrass Institude)  Probability seminar  
16:00  
Hicks Seminar Room J11  


Nov 16  Thu  Ieke Moerdijk (Sheffield)  Topology Reading Group  
13:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Nov 16  Thu  Callum Reader (Sheffield)  Topology Seminar  
16:00  Optimal Transport from Enriched Categories  
Hicks Seminar Room J11  
Abstract: Imagine we have a metric space whose points we think of as warehouses, and whose distances give the cost of moving a unit of stock. Now imagine we have two probability distributions that tell us how much stock is in each warehouse. A classical problem from optimal transport theory asks: how we might rearrange one distribution into another with minimal cost? The 'minimal cost' in this scenario defines a metric on the space of all probability measures, this metric is called earthmover's distance. Now instead of a metric space imagine we have a category enriched over the extended nonnegative reals. As Lawvere points out, these enriched categories can be thought of as generalised metric spaces. We show that from this perspective, probability measures might be thought of as functors and the natural transformation object that exists between them is actually equal to the earthmover's distance. What's more, we show that, when we take consider subprobability measures  that is, measures with total mass less than one  the natural transformation object improves on the earthmover's distance and can be intuited as the 'minimal cost of meeting demand'. 



Nov 17  Fri  Yannik Schuler (Sheffield)  
11:00  
Hicks Seminar Room J11  


Nov 17  Fri  Andrew Fisher, Constantinos Papachristoforou (Sheffield)  
16:00  
Hicks Seminar Room J11  


Nov 20  Mon  Jonathan Potts (Sheffield)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Nov 20  Mon  Richard Wilkinson (Nottingham)  Statistics Seminar  
15:00  Adjointaided inference for latent force models  
Hicks Seminar Room J11  
Abstract: Linear systems occur throughout engineering and the sciences, most notably as differential equations. In many cases the forcing function for the system is unknown, and interest lies in using noisy observations of the system to infer the forcing, as well as other unknown parameters. In this talk I will show how adjoints of linear systems can be used to efficiently infer forcing functions modelled as Gaussian processes. Adjoints have recently come to prominence in machine learning, but mainly as an approach to compute derivatives of cost functions for differential equation models. Here, we use adjoints in a different way that allows us to analytically compute the leastsquares estimator, or the full Bayesian posterior distribution of the unknown forcing. Instead of relying on solves of the original (forward model), we can recast the problem as n adjoint problems, where n is the number of data points. All that is required is the ability to solve adjoint systems numerically: it does not rely upon additional tractability of the linear system such as the ability to compute Green’s functions. We'll demonstrate this approach by inferring the pollution source in an advectiondiffusionreaction equation. 



Nov 21  Tue  Dan Graves (Leeds)  Astronomical Topology Working Group  
09:00  Topological Hochschild homology  
Hicks Seminar Room J11  
Abstract: I'll talk about THH for ring spectra, Tate spectra, the Frobenius and topological cyclic homology with a view towards understanding Proposition 1.1 in the Burklund, Hahn, Levy and Schlank preprint. 



Nov 21  Tue  Ieke Moerdijk (Sheffield)  Topology Reading Group  
12:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Nov 21  Tue  Robert Rockwood (Kings)  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Nov 21  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Nov 22  Wed  Paul Johnson (Sheffield)  Pure Maths Colloquium  
14:00  From Orbifold Hilbert schemes to Sec(x)  
Hicks Seminar Room J11  
Abstract: The Hilbert Scheme of points of n points in the plane is a smooth algebraic variety with a rich topology connected to partitions and representation theory. If G acts on a C^2, it also acts on the Hilbert scheme of points. The question of when certain G fixed point sets are nonempty winds up having a connection to zigzag permutations, which are counted by the Taylor series coefficients of Tan(x) and Sec(x). 



Nov 22  Wed  Jan Swart (Czech Academy of Sciences)  Probability seminar  
15:00  
Hicks Seminar Room J11  


Nov 22  Wed  Markus Fröb (Leipzig)  Cosmology, Relativity and Gravitation  
15:00  Invariant observables in quantum gravity and graviton loop corrections to the Hubble rate and the Newtonian potential  
Blackboard Collaborate  
Abstract: I present work done in the last years on the construction of dynamical coordinate systems for highly symmetric backgrounds, such as Minkowski, de Sitter, and FLRW cosmologies, and which are needed in the relational approach to construct gaugeinvariant observables in gravity. I show that it is possible to restrict the inevitable nonlocal contributions to the past light cone such that the obtained observables are causal. Lastly, I present some applications, namely the leading quantum gravitational corrections to the local expansion rate of our universe (the Hubble rate) and the Newtonian gravitational potential. Based on arXiv:1711.08470, arXiv:1806.11124, arXiv:2108.11960, arXiv:2109.09753, and arXiv:2303.16218 



Nov 23  Thu  Alberto Cobos Rabano (Sheffield)  The Sheffield Geometry and Physics Seminar  
10:00  Higher genus reduced GW invariants of projective space  
Hicks Seminar Room J11  
Abstract: The GromovWitten invariants of projective spaces are not enumerative in positive genera. The reason is geometric: the moduli space of genusg stable maps has several irreducible components, which contribute in the form of lowergenera GW invariants. In genus one, Vakil and Zinger constructed a blowup of the moduli space of stable maps and used it to define reduced GromovWitten invariants, which correspond to curvecounts in the main component. I will present a new definition of allgenera reduced GromovWitten invariants of complete intersections in projective spaces using desingularizations of sheaves. This is joint work with E. Mann, C. Manolache and R. Picciotto and can be found in arXiv:2310.06727. 



Nov 23  Thu  Kohei Iwaki (Tokyo )  The Sheffield Geometry and Physics Seminar  
11:30  Conifold gap property for the topological recursion free energy of an elliptic spectral curve  
Hicks Seminar Room J11  
Abstract: I’ll show that the topological recursion free energy of a family of elliptic spectral curves (which is related to Painlevé I through discrete Fourier transform) has a series expansion when a parameter tends to be large, and its leading term is written by the Bernoulli number. This shows the socalled conifold gap property in the above example. I’ll also explain a potential application of the result to the resurgence property. (Based on ongoing joint work with N. Iorgov, O. Lisovyy and Y. Zhuravlov.) 



Nov 23  Thu  Ieke Moerdijk (Sheffield)  Topology Reading Group  
13:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Nov 23  Thu  Yuqing Shi (MPIM Bonn)  Topology Seminar  
16:00  Costabilisation of telescopic spectral Lie algebras  
Hicks Seminar Room J11  
Abstract: One can think of the stabilisation of an ∞category as the ∞category of objects that admit infinite deloopings. For example, the ∞category of spectra is the stabilisation of the ∞category of homotopy types. Costabilisation is the opposite notion of stabilisation, where we are interested in objects that allow infinite desuspensions. It is easy to see that the costabilisation of the ∞category of homotopy types is trivial. Fix a prime number p. In this talk I will show that the costablisation of the ∞category of T(h)local spectral Lie algebras is equivalent to the ∞category of T(h)local spectra, where T(h) denotes a plocal telescope spectrum of height h. A key ingredient of the proof is to relate spectral Lie algebras to (spectral) Eₙ algebras via Koszul duality. 



Nov 23  Thu  Dmitrii Kolotkov (Warwick)  Plasma Dynamics Group  
16:00  NonAdiabatic MHD Seismology of the Solar Corona  
https://meet.google.com/iiujtngujm,  
Abstract: A powerful technique for the diagnostics of physical conditions in active regions of the Sun’s corona is the method of coronal seismology, based on observations of magnetohydrodynamic (MHD) wave processes in highresolution imaging data or indirectly as quasiperiodic pulsations in flaring light curves. Traditionally, coronal seismology is focused on the diagnostics of MHD properties of the Sun’s corona, such as the coronal magnetic field, plasma density, fine parallel and crossfield structuring, which are difficult to measure otherwise. In a series of recent works, it has been proven effective for probing not only MHD but also fundamental thermodynamic parameters of the coronal plasma through theoretical modelling and observations of MHD wave dynamics and stability in intrinsically nonadiabatic conditions and in the presence of a waveinduced thermal misbalance. In this talk, I present a few recent examples of the application of the method of nonadiabatic coronal seismology to probe such crucial parameters of the coronal plasma as energy transport coefficients, polytropic index, and heating function, regulating the delicate energy balance in the corona. More specifically, an apparent departure of the effective heat transfer coefficient from its classical Spitzer form is assessed seismologically under the assumptions of weak and full nonadiabaticity. The exact role of the effective polytropic index of the corona in the dynamics of nonadiabatic slow magnetoacoustic waves, its link with the effective thermal conduction coefficient, and shortcomings of the polytropic plasma approximation are discussed. I also show the potential of a recently developed theory of waveinduced thermal misbalance and a frequencydependent damping of slow magnetoacoustic waves for constraining the link between the coronal magnetic field and the heating function, which is not directly available in extreme ultraviolet or soft Xray observations traditionally used for coronal heating studies. 



Nov 27  Mon  TBA  The Sheffield Geometry and Physics Seminar  
10:00  
Hicks Seminar Room J11  


Nov 27  Mon  TBA  The Sheffield Geometry and Physics Seminar  
11:30  
Hicks Seminar Room J11  


Nov 27  Mon  Lewis Bartlett (Georgia)  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Nov 28  Tue  TBA  Astronomical Topology Working Group  
09:00  TBA  
Hicks Seminar Room J11  


Nov 28  Tue  Ieke Moerdijk (Sheffield)  Topology Reading Group  
12:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Nov 28  Tue  Johannes Girsch (Sheffield)  Number Theory seminar  
13:00  On families of degenerate representations of GL_n(F)  
Hicks Seminar Room J11 / Google Meet  
Abstract: Smooth generic representations of GL_n(F), i.e. representations admitting a nondegenerate Whittaker model, are an important class of representations, for example in the setting of RankinSelberg integrals. However, in recent years there has been an increased interest in nongeneric representations and their degenerate Whittaker models. By the theory of BernsteinZelevinsky derivatives we can associate to each smooth irreducible representation of GL_n(F) an integer partition of n, which encodes the "degeneracy" of the representation. For each integer partition \lambda of n, we then construct a family of universal degenerate representations of type \lambda and prove some suprising properties of these families. This is joint work with David Helm. 



Nov 28  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  


Nov 28  Tue  Sofia Dias (York)  RSS Seminar  
16:00  Evidence synthesis for decision making: making best use of relevant evidence  
Online / https://rss.org.uk/trainingevents/events/events2023/localgroups/agmwebinarevidencesynthesisfordecisionmaking/  
Abstract: Preceded by Local Group AGM Metaanalyses are typically used to pool evidence from multiple studies in order to decide which treatment is most effective or costeffective, out of several alternatives. When deciding which treatments to recommend for use in a national health service, we typically start with a welldefined decision problem specifying the patient population, interventions and outcomes of interest. A search of the literature for randomised controlled trials (RCTs) comparing the interventions of interest then follows, where evidence is collected and assessed for quality and relevance to the decision problem. Often evidence from available RCTs that does not exactly match our decision problem is classed as not directly applicable to the decisionproblem (indirect evidence) and discarded. However, models that allow incorporation of such "indirect" evidence using reasonable assumptions may reduce uncertainty in estimates of treatment effectiveness, leading to better decisions. Network metaanalysis (NMA) extended the idea of pairwise metaanalysis to pool evidence on more than one intervention, allowing for indirect evidence on additional treatment comparisons to be incorporated. Whilst standard NMA methods are now well established, some recent extensions allow pooling of additional data, reducing uncertainty. After briefly introducing the principles of metaanalysis and NMA, the extension of NMA models to incorporate doseresponse relationships will be described. Using examples, we will show how evidence on different doses of interventions can be combined to strengthen inferences and how key modelling assumptions can be checked. Some additional methodological extensions that allow other types of "indirect" evidence to be incorporated will also be outlined. 



Nov 29  Wed  Veronique Fischer (University of Bath)  Pure Maths Colloquium  
14:00  SubRiemannian quantum limits  
Hicks Seminar Room J11  
Abstract: We will start with a short discussion on semiclassical analysis to introduce the concept of quantum limits. We will present an overview of subRiemannian geometry and the recent developments of spectral geometry in this context, especially quantum limits on nilpotent Lie groups. 



Nov 29  Wed  Manuel Reichert (Sussex)  Cosmology, Relativity and Gravitation  
15:00  From fluctuating gravitons to Lorentzian quantum gravity  
Hicks Seminar Room J11  
Abstract: I will review recent progress in the asymptotic safety approach to quantum gravity. This includes the computation of momentumdependent graviton correlation functions, the phase structure of the Standard Model of Particle Physics with asymptotically safe gravity, and the first computation directly in spacetimes with Lorentzian signatures via the spectral function of the graviton. 



Nov 30  Thu  Ieke Moerdijk (Sheffield)  Topology Reading Group  
13:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Nov 30  Thu  Fiona Torzewska (Bristol)  Topology Seminar  
16:00  Motion groupoids  
Hicks Seminar Room J11  
Abstract: The braiding statistics of point particles in 2dimensional topological phases are given by representations of the braid groups. One approach to the study of generalised particles in topological phases, loop particles in 3dimensions for example, is to generalise (some of) the several different realisations of the braid group. In this talk I will construct for each manifold M its motion groupoid $Mot_M$, whose object class is the power set of M. I will discuss several different, but equivalent, quotients on motions leading to the motion groupoid. In particular that the quotient used in the construction $Mot_M$ can be formulated entirely in terms of a level preserving isotopy relation on the trajectories of objects under flows  worldlines (e.g. monotonic `tangles'). I will also give a construction of a mapping class groupoid $\mathrm{MCG}_M$ associated to a manifold M with the same object class. For each manifold M I will construct a functor $F \colon Mot_M \to MCG_M$, and prove that this is an isomorphism if $\pi_0$ and $\pi_1$ of the appropriate space of selfhomeomorphisms of M is trivial. In particular there is an isomorphism in the physically important case $M=[0,1]^n$ with fixed boundary, for any $n\in\mathbb{N}$. I will discuss several examples throughout. 



Dec 4  Mon  TBC  Mathematical Biology Seminar  
13:00  
Hicks Seminar Room J11  


Dec 5  Tue  Ieke Moerdijk (Sheffield)  Topology Reading Group  
12:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Dec 5  Tue  Chris Birkbeck (UEA)  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Dec 5  Tue  TBA  Algebra / Algebraic Geometry seminar  
14:30  
Hicks Seminar Room J11  


Dec 7  Thu  Ieke Moerdijk (Sheffield)  Topology Reading Group  
13:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Dec 7  Thu  Lukas Brantner (Oxford)  Topology Seminar  
16:00  
Hicks Seminar Room J11  


Dec 11  Mon  Ivan Tulli (Sheffield)  The Sheffield Geometry and Physics Seminar  
10:00  Variations of BPS structures, quaternionicKähler metrics and Sduality  
Hicks Seminar Room J11  
Abstract: Inspired by constructions in CalabiYau compactifications of type IIA/B string theory, we explain how to construct quaternionicKähler (QK) manifolds from certain special variations of BPS structures. We furthermore specify a subclass of such QK metrics admitting a rather nontrivial SL(2,Z) action by isometries, related to Sduality in type IIB string theory. Along the way, we comment on relations to the TBA equations from GaiottoMooreNeitzke, and joint work with M. Alim, A. Saha and J. Teschner. This is joint work with V. Cortés (arXiv:2105.09011, arXiv:2306.01463) based on several works in the physics literature by S. Alexandrov, D. Persson, B. Pioline, F. Saueressig, S. Vandoren and many more. 



Dec 11  Mon  Nicholas Williams (Lancaster)  The Sheffield Geometry and Physics Seminar  
11:30  DonaldsonThomas invariants for the BridgelandSmith correspondence  
Hicks Seminar Room J11  
Abstract: Celebrated work of Bridgeland and Smith shows a correspondence between quadratic differentials on Riemann surfaces and stability conditions on certain 3CalabiYau triangulated categories. Part of this correspondence is that finitelength trajectories of the quadratic differential correspond to categories of semistable objects of a fixed phase. Categories of semistable objects have an associated DonaldsonThomas invariant which, in some sense, counts the objects in the category. Work of Iwaki and Kidwai predicts particular values for these DonaldsonThomas invariants for different types of finitelength trajectories, based on the output of topological recursion. The DonaldsonThomas invariants produced by the category of Bridgeland and Smith do not always match these predictions. However, we show that if one replaces this category by the category recently studied by Christ, Haiden, and Qiu, then one does obtain the DonaldsonThomas invariants matching the predictions. This is joint work with Omar Kidwai. 



Dec 12  Tue  Ieke Moerdijk (Sheffield)  Topology Reading Group  
12:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Dec 12  Tue  TBA  Number Theory seminar  
13:00  
Hicks Seminar Room J11 / Google Meet  


Dec 13  Wed  Ana Alonso Serrano (AEI Potsdam)  Cosmology, Relativity and Gravitation  
15:00  
Blackboard Collaborate  


Dec 14  Thu  Ieke Moerdijk (Sheffield)  Topology Reading Group  
13:00  (Co)homology of categories and functor (co)homology  
Hicks Seminar Room J11  


Dec 14  Thu  Simon Willerton (Sheffield)  Topology Seminar  
16:00  
Hicks Seminar Room J11  


Jan 31  Wed  William Giare (Sheffield)  Cosmology, Relativity and Gravitation  
15:00  
Hicks Seminar Room J11  

