Oct 28 (Wed)
11:00 MJC2006 ApplAvishek Das (Durham University): Mechano-chemical information processing in living matter
Computations performed by biological cells and tissues are unique - they have a low energy cost and are robust to noise. What is the physical origin of such intelligence? Often, it emerges from a coupling of chemical reaction networks with mechanical degrees of freedom, covering multiple timescales. My group uses theory and computations to investigate the optimal designs of such information-processing motifs in soft and living matter. For this, we combine statistical physics with information theory.
In this talk, I will discuss two recent advancements through this approach. The first is on quantifying the information transmission between pairs of stochastic variables in complex systems. I will discuss a computational algorithm, called Transfer Entropy - Path Weight Sampling (TE-PWS), that makes it possible to exactly quantify the directional information transmission ('transfer entropy') in general stochastic systems for the first time. The second part of the talk will be on how analytical theory and numerical simulations can together reveal the biological function of information, with experimentally testable predictions. As an example, I will discuss stochastic navigators, i.e., autonomous agents that sense and swim with noise, such as chemotactic cells. Here, I will show that information feedback from the cell to its environment due to its own swimming is a central aspect of navigation, that there exists an optimal feedback information in bits, and that information is necessary but not always sufficient for navigation.
Venue: MJC2006
13:00 MCS3070 GSymOscar Lewis (University of Oxford): Dynamical Interpolation Between Continuous SymTFTs
Using holography, we explain the origin of the dynamical gauging map put forward by Antinucci & Benini (2024) to dynamically gauge $U(1)$ symmetries within the SymTFT framework. We show how the SymTFTs before and after the gauging are naturally extracted from the zero and infinite coupling limits of a bulk Maxwell theory, respectively, only after a projection onto the photon vacuum. The coupling limits of the Maxwell Dirichlet and Neumann boundary conditions will be explained, as well as the interpretation of bulk defects on the boundary. Our framework naturally extends beyond ordinary Maxwell theory to capture both anomalies and dynamical gauging in systems with multiple $U(1)$ symmetries. After discussing some illustrative examples of this procedure, we comment on how our work naturally fits into the SymTFT from descent framework. Based on upcoming joint work with Andrea Antinucci.
Venue: MCS3070
Online: None
Oct 29 (Thu)
13:00 Online o E&PDr Katie Steckles (Manchester Metropolitan University): Two-Stage Exams - implementing group assessment in an exam setting
14:00 MCS2068 ASGMark Chambers (Sheffield): (Square-roots of) Algebraic L-Values, and Congruences
Conjecturally, the special values of L-functions should encode interesting arithmetic information, though little is known or understood. However, one of the main methods of progress has been to study them via congruences. In this talk, we consider the twisted L-values attached to a modular form and a character, and examine how congruences mod \(\ell\) to other modular forms can "explain" when these values are divisible by \(\ell\). In the case of quadratic twists of central L-values, we then refine this to consider square roots of L-values. This allows us to prove cases when \(\ell^2\) divides a central L-value, which should conjecturally be explained by elements in Tate-Shafarevich groups. This is done by considering cohomological theta lifts to half-integral weight.
Venue: MCS2068
Oct 30 (Fri)
13:00 MCS2068 HEPMRuth Gregory (King's College London): Accelerating Black Holes
An accelerating black hole in GR is described by the C-metric, a spacetime with a deformed horizon and a cosmic string connecting the black hole to asymptotic infinity meaning the black hole is part of a composite system. I show how to describe the thermodynamics of the system, including changes in the string tension. I will also highlight recent progress on acceleration and rotation in three dimensions, including accelerating "point particles" as well as BTZ-like solutions.
Venue: MCS2068
14:00 MCS2068 G&TFrancesco Lin (Columbia): Coexact 1-form spectral gaps and three-dimensional topology
The spectral gap of the Hodge Laplacian on coexact 1-forms
is a fundamental quantity associated to a Riemannian manifold which has
attracted quite a lot of attention in recent years. I will begin by
discussing the role it plays in topological problems about
three-manifolds (such as the existence on taut foliations on rational
homology spheres) via its relation with Floer theoretic invariants.
Motivated by this, I will then focus on the case of hyperbolic
manifolds, and describe techniques to determine explicitly such spectral
gaps in concrete examples (including certain infinite families). This is
joint work with M. Lipnowski.
Venue: MCS2068
Nov 02 (Mon)
13:00 MCS2068 ProbThomas Hughes (University of Bath): Fluctuations for fully pushed stochastic fronts
This talk concerns travelling wave solutions to stochastic reaction diffusion equations, such as those arising in population genetics to model the genetic composition of an evolving spatial population. Different reaction terms are expected to correspond to three types of travelling waves pushed, semi-pushed, and pulled which exhibit different behaviours under noisy perturbation. I will discuss a recent work examining the behaviour of the front in the (fully) pushed regime, which includes both bi-stable and mono-stable reactions. Our main result precisely characterizes the limiting deviation of the position of the front from its "deterministic" position, in a certain scaling regime, as a Brownian motion with drift.
This is joint work with Alison Etheridge, Raphaël Forien and Sarah Penington.
Venue: MCS2068
16:00 MCS2068 PureFrancesco Lin (Columbia): Hyperbolic geometry in dimension two, three and above (especially four)
After introducing the basics of hyperbolic geometry in all
dimensions, I will highlight some of the key features that make
hyperbolic manifolds behave very differently in dimension two, three,
and at least four. I will then focus on some interesting open problems
about the topology of hyperbolic four-manifolds, and discuss some recent
results regarding symplectic structures obtained in joint work with B.
Martelli.
Venue: MCS2068
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Usual Venue: MCS3070
Contact: andrew.krause@durham.ac.uk
Oct 28 11:00 Avishek Das (Durham University): Mechano-chemical information processing in living matter
Computations performed by biological cells and tissues are unique - they have a low energy cost and are robust to noise. What is the physical origin of such intelligence? Often, it emerges from a coupling of chemical reaction networks with mechanical degrees of freedom, covering multiple timescales. My group uses theory and computations to investigate the optimal designs of such information-processing motifs in soft and living matter. For this, we combine statistical physics with information theory.
In this talk, I will discuss two recent advancements through this approach. The first is on quantifying the information transmission between pairs of stochastic variables in complex systems. I will discuss a computational algorithm, called Transfer Entropy - Path Weight Sampling (TE-PWS), that makes it possible to exactly quantify the directional information transmission ('transfer entropy') in general stochastic systems for the first time. The second part of the talk will be on how analytical theory and numerical simulations can together reveal the biological function of information, with experimentally testable predictions. As an example, I will discuss stochastic navigators, i.e., autonomous agents that sense and swim with noise, such as chemotactic cells. Here, I will show that information feedback from the cell to its environment due to its own swimming is a central aspect of navigation, that there exists an optimal feedback information in bits, and that information is necessary but not always sufficient for navigation.
Venue: MJC2006
Usual Venue: MCS2068
Contact: johannes.girsch@durham.ac.uk
Oct 29 14:00 Mark Chambers (Sheffield): (Square-roots of) Algebraic L-Values, and Congruences
Conjecturally, the special values of L-functions should encode interesting arithmetic information, though little is known or understood. However, one of the main methods of progress has been to study them via congruences. In this talk, we consider the twisted L-values attached to a modular form and a character, and examine how congruences mod \(\ell\) to other modular forms can "explain" when these values are divisible by \(\ell\). In the case of quadratic twists of central L-values, we then refine this to consider square roots of L-values. This allows us to prove cases when \(\ell^2\) divides a central L-value, which should conjecturally be explained by elements in Tate-Shafarevich groups. This is done by considering cohomological theta lifts to half-integral weight.
Venue: MCS2068
Nov 05 14:00 David Helm (Imperial): TBA
Nov 12 14:00 Fredrik Stromberg (Nottingham): TBA
Nov 26 14:00 Sean Dewar (KU Leuven): TBA
Dec 03 14:00 Justin Trias (Aix-Marseille Universite): TBA
Jan 21 14:00 Shaun Stevens (UEA): TBA
Feb 04 14:00 Andrew Graham (Oxford): TBA
Feb 18 14:00 Akshat Mugdal (Warwick): TBA
Feb 25 14:00 Sean Cotner (Bonn): TBA
Usual Venue: OC218
Contact: mohamed.anber@durham.ac.uk
For more information, see HERE.
No upcoming seminars have been scheduled (not unusual outside term time).
Usual Venue: MCS3052
Contact: andrew.krause@durham.ac.uk
Oct 29 13:00 Dr Katie Steckles (Manchester Metropolitan University): Two-Stage Exams - implementing group assessment in an exam setting
At Manchester Metropolitan University, we have been trialling a new form of assessment (on the maths course and elsewhere), which splits a three-hour invigilated exam into a two-hour individual exam and a one-hour group-based exam. This two-stage exam gives the students a lower-stakes opportunity to improve their mark and builds a collaborative aspect into their learning and assessment. The approach aims to reduce anxiety, and to make the results of the assessment more reflective of real-world working ability. I will share how weve implemented this so far at Manchester Met, and what the results and feedback from students have been, as well as some of the challenges weve faced.
Venue: Online only
Usual Venue: MCS3070
Contact: yi-lok-enoch.leung@durham.ac.uk
Oct 28 13:00 Oscar Lewis (University of Oxford): Dynamical Interpolation Between Continuous SymTFTs
Using holography, we explain the origin of the dynamical gauging map put forward by Antinucci & Benini (2024) to dynamically gauge $U(1)$ symmetries within the SymTFT framework. We show how the SymTFTs before and after the gauging are naturally extracted from the zero and infinite coupling limits of a bulk Maxwell theory, respectively, only after a projection onto the photon vacuum. The coupling limits of the Maxwell Dirichlet and Neumann boundary conditions will be explained, as well as the interpretation of bulk defects on the boundary. Our framework naturally extends beyond ordinary Maxwell theory to capture both anomalies and dynamical gauging in systems with multiple $U(1)$ symmetries. After discussing some illustrative examples of this procedure, we comment on how our work naturally fits into the SymTFT from descent framework. Based on upcoming joint work with Andrea Antinucci.
Venue: MCS3070
Nov 23 10:00 Benjamin Muntz (University of Nottingham): TBA
Dec 09 13:00 Alonso Perez-Lona (Max Planck Institute for Mathematics in the Sciences): TBA
Usual Venue: MCS2068
Contact: martin.p.kerin@durham.ac.uk
Oct 30 14:00 Francesco Lin (Columbia): Coexact 1-form spectral gaps and three-dimensional topology
The spectral gap of the Hodge Laplacian on coexact 1-forms
is a fundamental quantity associated to a Riemannian manifold which has
attracted quite a lot of attention in recent years. I will begin by
discussing the role it plays in topological problems about
three-manifolds (such as the existence on taut foliations on rational
homology spheres) via its relation with Floer theoretic invariants.
Motivated by this, I will then focus on the case of hyperbolic
manifolds, and describe techniques to determine explicitly such spectral
gaps in concrete examples (including certain infinite families). This is
joint work with M. Lipnowski.
Venue: MCS2068
Nov 06 14:00 Dirk Schütz (Durham): Khovanov homology of 3-braids
Khovanov homology of a link tends to contain a lot of
torsion of order 2, although torsion of higher order does occasionally
occur. In this talk we prove a conjecture of Przytycki and Sazdanovi\u0107
that the Khovanov homology of the closure of a 3-braid only contains
torsion of order 2. Our techniques also show that the Knight-Move
Conjecture, a conjecture which is known to be false in general, holds
for 3-braids. Time permitting, we will also describe a polynomial-time
algorithm to compute the Khovanov homology of a 3-braid.
Venue: MCS2068
Nov 13 14:00 Michael Kohn (Durham): \( \mathfrak{sl}_p \)-homology over \( \mathbb{F}_p \)
\( \mathfrak{sl}_N \) homology is a quantum invariant of
knots and links, generalising Khovanov homology. In this talk we will
provide a brief introduction to how this is defined via objects called
foams. We will also introduce s-invariants, which have applications in
4-manifold topology. We will then show that for the case of N a prime p,
and working over \( \mathbb{F}_p \), the chain complex that this theory
associates to a link diagram has a remarkably simple decomposition. From
this, we can deduce new results and reprove existing results regarding
s-invariants and the structure of \( \mathfrak{sl}_p \) homology.
Venue: MCS2068
Nov 20 14:00 Luke Jeffreys (Bristol): TBA
Nov 20 15:00 Philipp Bartmann (Potsdam): TBA
Nov 27 14:00 Emily Roff (Edinburgh): TBA
Dec 04 14:00 Simon Willerton (Sheffield): TBA
Jan 29 14:00 Marco Radeschi (Torino): TBA
Feb 12 14:00 Kasia Wyczesany (Leeds): TBA
Usual Venue: MCS2068
Contact: p.e.dorey@durham.ac.uk,parita.r.shah@durham.ac.uk,tobias.p.hansen@durham.ac.uk
Oct 30 13:00 Ruth Gregory (King's College London): Accelerating Black Holes
An accelerating black hole in GR is described by the C-metric, a spacetime with a deformed horizon and a cosmic string connecting the black hole to asymptotic infinity meaning the black hole is part of a composite system. I show how to describe the thermodynamics of the system, including changes in the string tension. I will also highlight recent progress on acceleration and rotation in three dimensions, including accelerating "point particles" as well as BTZ-like solutions.
Venue: MCS2068
Nov 06 13:00 Hugh Osborn (Cambridge University): TBA
Nov 13 13:00 Anton Kapustin (Caltech): Locality, higher symmetries, and anomalies: an operator-algebraic approach
In the usual Euclidean path-integral picture, higher symmetries are represented by invertible topological defects, and ’t Hooft anomalies are described by anomaly inflow from a topological action in one dimension higher. Is there a corresponding construction that starts directly from the algebra of local operators and its symmetries? To address this question, I will describe a mathematically precise framework based on localized symmetry transformations and their commutators. To each spatial region U, one associates a group of transformations localized in U. Locality implies that the commutator of transformations localized in regions U and V is localized in their intersection. From these data one can extract a system of higher groups, one per cover of space. Both anomalies and higher symmetries are encoded in this system of higher groups. The framework is designed to treat algebraic QFT and quantum lattice systems in a common language. The guiding idea is that topology emerges from the interplay of symmetry and locality.
Venue: MCS2068
Nov 20 13:00 Prahar Mitra (Southampton University): TBA
Nov 27 13:00 Mariana Carrillo Gonzalez (Southampton University): TBA
Dec 04 13:00 Daniel Brennan (University of Birmingham): TBA
Dec 11 13:00 Alessandro Georgoudis (Queen Mary University of London): TBA
Usual Venue: MCS2068
Contact: tyler.helmuth@durham.ac.uk,oliver.kelsey-tough@durham.ac.uk
Nov 02 13:00 Thomas Hughes (University of Bath): Fluctuations for fully pushed stochastic fronts
This talk concerns travelling wave solutions to stochastic reaction diffusion equations, such as those arising in population genetics to model the genetic composition of an evolving spatial population. Different reaction terms are expected to correspond to three types of travelling waves pushed, semi-pushed, and pulled which exhibit different behaviours under noisy perturbation. I will discuss a recent work examining the behaviour of the front in the (fully) pushed regime, which includes both bi-stable and mono-stable reactions. Our main result precisely characterizes the limiting deviation of the position of the front from its "deterministic" position, in a certain scaling regime, as a Brownian motion with drift.
This is joint work with Alison Etheridge, Raphaël Forien and Sarah Penington.
Venue: MCS2068
Nov 09 13:00 Eleanor Archer (Université Paris Dauphine - PSL): Limits of massive spanning forests
The lambda spanning forest of a graph G is a random subgraph that generalises the notion of the uniform spanning tree. It was recently shown by D'Achille, Enriquez and Melotti that on the complete graph with n vertices, these forests admit a (local) limit as n goes to infinity. This limit can fall into three regimes depending on whether the parameter lambda grows faster than, slower than, or at the same rate as n. We generalise their result to show that the same limits appear for any sequence of (almost) regular graphs with degrees tending to infinity, provided that lambda is tuned correctly as a function of the degree parameter.
The proof exploits fundamental links between uniform spanning trees and loop-erased random walks. This joint work with Breki Pálsson (University of Iceland).
Venue: MCS2068
Nov 12 14:00 Quentin Berger (Université Sorbonne Paris Nord): 2D directed polymers, the Stochastic Heat Flow and the KPZ equation
I will review some of the progress on the directed polymer model in dimension d=2, whose partition functions can be seen as a discretised version of the stochastic heat equation. Recent results have shown that, in a suitable (and subtle) critical window of parameters, the model converges to a disordered limit, namely the Critical 2D Stochastic Heat Flow (SHF) introduced by Caravenna, Sun and Zygouras. This SHF is a non-Gaussian stochastic process of measures on R^2, and a lot of its properties have been studied over the last years. In this talk, I will first take some time to explain the (idea of the) construction of the SHF and then review some of the recent advances on its relation to the KPZ equation.
Venue: Scott Logic
Nov 16 13:00 Khoa Le (University of Leeds): Regularization by Fractional Noise for Differential Equations with Singular Drift
We study differential equations with time-dependent drifts that are merely integrable in space and time, driven by additive fractional Brownian motion with Hurst parameter H<1/2. Although the corresponding deterministic equations may be highly non-unique, the irregularity of the noise restores strong well-posedness. Under a natural subcriticality condition on the space-time integrability of the drift, together with conditions required for a change-of-measure argument, we prove strong existence and path-by-path uniqueness. We also obtain quantitative stability with respect to the initial condition and the drift, both pathwise and in moment norms, and construct a Hölder-continuous semiflow. As H approaches 1/2, the admissible regime recovers, up to an endpoint, the classical Brownian scaling condition of Krylov and Röckner (2005). I will explain the main ideas of the proof, which combine stochastic sewing, Lyons' rough-path estimates, and a quantitative John-Nirenberg inequality for stochastic processes with vanishing oscillations. Base on a joint work with Oleg Butkovsky and Toyomu Matsuda.
Venue: MCS2068
Nov 23 13:00 Michael Magee (University of Durham):
Dec 07 13:00 Mateusz Piorkowski (University of Durham):
Usual Venue: MCS2068
Contact: alexander.mangerel@durham.ac.uk
Nov 02 16:00 Francesco Lin (Columbia): Hyperbolic geometry in dimension two, three and above (especially four)
After introducing the basics of hyperbolic geometry in all
dimensions, I will highlight some of the key features that make
hyperbolic manifolds behave very differently in dimension two, three,
and at least four. I will then focus on some interesting open problems
about the topology of hyperbolic four-manifolds, and discuss some recent
results regarding symplectic structures obtained in joint work with B.
Martelli.
Venue: MCS2068
Nov 17 13:00 Joel Moreira (Warwick): TBA
Nov 24 13:00 Giannis Platis (Patras): TBA
Dec 01 13:00 Rob Kurinczuk (Sheffield): TBA
Jan 27 13:00 Marco Radeschi (Torino): TBA
Feb 09 13:00 Tim Browning (UCL): TBA
Feb 23 13:00 Tara Brendle (Glasgow): TBA
Mar 16 13:00 Rémi Coulon (Dijon): TBA
Usual Venue: MCS3070
Contact: joe.thomas@durham.ac.uk
No upcoming seminars have been scheduled (not unusual outside term time).
