Oct 02 (Fri)
13:00 MCS0001 HEPMIgor Klebanov (Princeton University): Landau-Ginzburg Description of Some Minimal Conformal Models
The minimal conformal models M(p,q) were introduced 43 years ago in a landmark paper by Belavin, Polyakov and Zamolodchikov. Their work provided a "machine" for solving a set of conformal field theories, but the Landau-Ginzburg effective Lagrangians for many of them are still unknown. We review some recent progress on non-unitary minimal models, which are described by PT-symmetric cubic Lagrangians. We also discuss the N=1 supersymmetric minimal models. One of them is special in that it has super-W3 symmetry. We suggest a very simple field theory description of this model using two superfields with a cubic superpotential.
Venue: MCS0001
Oct 05 (Mon)
13:00 MCS2068 ProbXusheng Zhang (Durham (CS)): Low temperature random Cluster Model on Trees and Random Graphs
In this talk, I will discuss the low-temperature random-cluster model on trees and tree-like random graphs, a dependent percolation model closely related to the Ising and Potts models. I will describe a second uniqueness threshold on the wired regular tree, resolving a conjecture of Haggstrom from 1996, and explain how this threshold is tied to decay of correlations under wired boundary conditions. I will then discuss consequences for dynamics: near-optimal mixing of random-cluster Glauber dynamics on wired trees, and on random regular graphs in the low temperature uniqueness regime. These results give efficient sampling algorithms for the random-cluster and Potts models on treelike graphs. Based on joint work with A. Blanca, R. Gheissari, and H. Park.
Venue: MCS2068
Oct 06 (Tue)
14:00 MCS2068 APDECatherine Drysdale (Lancaster University): The Mathematics of Depression
In this talk, I will talk about the research that motivated my fellowship that brings together brain network and hormones in the case of the mental illness depressions. In my approach, I consider brain networks as directed graphs and hormone networks as systems of DDEs that are linked via the hippocampus. I give examples where techniques such as pseudospectra can be used to understand perturbations of biological rhythms. I will also speak to the challenges of data-integration and mapping together different brain imaging modalities.
Venue: MCS2068
Oct 07 (Wed)
16:00 zoom A&CJiajie Mei (University of Amsterdam): All-Plus QED Wavefunctions in de Sitter Space
I will discuss tree-level wavefunction coefficients in scalar QED in four-dimensional de Sitter space, focusing on a charged scalar pair coupled to an arbitrary number of positive-helicity photons. We find a simple all-multiplicity structure for these coefficients. I will present the resulting compact formula and explain how its analytic structure, Abelian Ward identities, and conformal symmetry lead to an exact recursion.
Venue: zoom
Online: https://teams.microsoft.com/meet/355232082425514?p=EwRqKZ5cRmTo7X2dIq
Oct 09 (Fri)
13:00 MCS2068 HEPMDaniele Bielli (Durham University): TBA
14:00 MCS2068 G&TAdam Barber (Durham): Inscriptions of Isosceles Trapezoids in Jordan Curves
The classical example of an inscription problem is the
Square Peg Problem, which asks whether every Jordan curve contains four
points which are the vertices of a square. A natural generalisation is
to consider inscriptions of polygons in Jordan curves. We will motivate
why isosceles trapezoids are currently the most interesting class of
polygons to ask this question for and introduce new results in this
direction. The talk is based on the paper of the same name, which
extends the work of Andrew Lobb and Josh Greene on rectangles to the
case of isosceles trapezoids.
Venue: MCS2068
Click on title to see abstract.
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These events are hosted in and/or organised by members of the Department (follow links for details):
Oct 16 [Kenworthy Hall, St Mary's] Willmore Day 2026
Speakers: A Barber, L Dahlmeier, D Disney, S Mohapatra, J Quijas, F Salerno, S Shepherd
Venue: Kenworthy Hall, St Mary's at/from 09:30
Click on series to expand.
Contact: arthur.lipstein@durham.ac.uk
Oct 07 16:00 Jiajie Mei (University of Amsterdam): All-Plus QED Wavefunctions in de Sitter Space
I will discuss tree-level wavefunction coefficients in scalar QED in four-dimensional de Sitter space, focusing on a charged scalar pair coupled to an arbitrary number of positive-helicity photons. We find a simple all-multiplicity structure for these coefficients. I will present the resulting compact formula and explain how its analytic structure, Abelian Ward identities, and conformal symmetry lead to an exact recursion.
Venue: zoom
Usual Venue: MCS2068
Contact: yohance.a.osborne@durham.ac.uk
Oct 06 14:00 Catherine Drysdale (Lancaster University): The Mathematics of Depression
In this talk, I will talk about the research that motivated my fellowship that brings together brain network and hormones in the case of the mental illness depressions. In my approach, I consider brain networks as directed graphs and hormone networks as systems of DDEs that are linked via the hippocampus. I give examples where techniques such as pseudospectra can be used to understand perturbations of biological rhythms. I will also speak to the challenges of data-integration and mapping together different brain imaging modalities.
Venue: MCS2068
Oct 13 14:00 Phoebe Valentine (University of Warwick): Characterising 1-rectifiable metric spaces via connected tangent spaces
Characterising rectifiability using the existence of tangents is a very classical technique in GMT and positive results can be found even when using very weak notions of a tangent. This work goes further to only require that tangents are supported on a connected set. Despite this weak requirement, we can still prove that 1-rectifiability in complete metric spaces is implied by the existence of connected tangents almost everywhere. This, combined with prior results of Bate, establishes a characterisation of 1-rectifiability in complete metric spaces, which is in particular also new for Euclidean space. Inspired by geometric ideas from Besicovitch in the plane, we achieve our result by exploiting the inherent gappiness of purely 1-unrectifiable sets. To this end, we will give rigorous meaning to this 'gappiness' and show how it may be quantified.
Venue: MCS2068
Oct 20 14:00 Ofelia Bonesini (London School of Economics): Continuous-time persuasion by filtering
We frame dynamic persuasion in a partial observation stochastic control Leader-Follower game with an ergodic criterion. The Receiver controls the dynamics of a multidimensional unobserved state process. Information is provided to the Receiver through a device designed by the Sender that generates the observation process. The commitment of the Sender is enforced. We develop this approach in the case where all dynamics are linear and the preferences of the Receiver are linear-quadratic. We prove a verification theorem for the existence and uniqueness of the solution of the HJB equation satisfied by the Receiver's value function. An extension to the case of persuasion of a mean field of interacting Receivers is also provided. We illustrate this approach in two applications: the provision of information to electricity consumers with a smart meter designed by an electricity producer; the information provided by carbon footprint accounting rules to companies engaged in a best-in-class emissions reduction effort. In the first application, we link the benefits of information provision to the mispricing of electricity production. In the latter, we show that even in the absence of information cost, it might be optimal for the regulator to blur information available to firms to prevent them from coordinating on a higher level of carbon footprint to reduce their cost of reaching a below average emission target. This is a joint work with René Aïd, Giorgia Callegaro and Luciano Campi.
Venue: MCS2068
Oct 27 14:00 Dante Kalise (Imperial College London): Stabilising Feedback Laws for Mean-Field Control and Global Optimisation
We look at feedback control of large systems of interacting particles. In the mean-field limit, this becomes the stabilisation of McKeanVlasov PDEs. When the free energy is non-convex, the target states may be unstable or reached only very slowly. We linearise the Wasserstein gradient flow around the target and act on its finitely many slow or unstable modes. This gives a Riccati feedback law that locally exponentially stabilises the full nonlinear dynamics, and it can be seen as a local convexification of the free energy.
The same idea applies to consensus-based optimisation (CBO), which is itself a McKeanVlasov particle system whose target is the global minimiser. We treat global optimisation as an optimal stabilisation problem and add a stabilising feedback, obtained from the associated HJB equation, to the CBO dynamics. Convergence becomes faster and more robust, including in high dimensions.
Based on joint works with M. Herty, Y. Huang, N. Kantas, H. Kouhkouh, L. Moschen and G. A. Pavliotis.
Venue: MCS2068
Usual Venue: MCS3070
Contact: andrew.krause@durham.ac.uk
No upcoming seminars have been scheduled (not unusual outside term time).
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
No upcoming seminars have been scheduled (not unusual outside term time).
Usual Venue: MCS2068
Contact: martin.p.kerin@durham.ac.uk
Oct 09 14:00 Adam Barber (Durham): Inscriptions of Isosceles Trapezoids in Jordan Curves
The classical example of an inscription problem is the
Square Peg Problem, which asks whether every Jordan curve contains four
points which are the vertices of a square. A natural generalisation is
to consider inscriptions of polygons in Jordan curves. We will motivate
why isosceles trapezoids are currently the most interesting class of
polygons to ask this question for and introduce new results in this
direction. The talk is based on the paper of the same name, which
extends the work of Andrew Lobb and Josh Greene on rectangles to the
case of isosceles trapezoids.
Venue: MCS2068
Oct 23 14:00 Yuri Santos Rego (Lincoln): TBA
Oct 30 14:00 Dirk Schütz (Durham): TBA
Nov 06 14:00 David Lanners (Durham): TBA
Nov 20 14:00 Luke Jeffreys (Bristol): TBA
Nov 20 15:00 Philipp Bartmann (Potsdam): TBA
Nov 27 14:00 Emily Roff (Edinburgh): 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 02 13:00 Igor Klebanov (Princeton University): Landau-Ginzburg Description of Some Minimal Conformal Models
The minimal conformal models M(p,q) were introduced 43 years ago in a landmark paper by Belavin, Polyakov and Zamolodchikov. Their work provided a "machine" for solving a set of conformal field theories, but the Landau-Ginzburg effective Lagrangians for many of them are still unknown. We review some recent progress on non-unitary minimal models, which are described by PT-symmetric cubic Lagrangians. We also discuss the N=1 supersymmetric minimal models. One of them is special in that it has super-W3 symmetry. We suggest a very simple field theory description of this model using two superfields with a cubic superpotential.
Venue: MCS0001
Oct 09 13:00 Daniele Bielli (Durham University): TBA
Oct 16 13:00 Joaquin Liniado (Edinburgh University): TBA
Oct 23 13:00 Enoch Leung (Durham University): TBA
Oct 30 13:00 Ruth Gregory (Kings College London): TBA
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
Oct 05 13:00 Xusheng Zhang (Durham (CS)): Low temperature random Cluster Model on Trees and Random Graphs
In this talk, I will discuss the low-temperature random-cluster model on trees and tree-like random graphs, a dependent percolation model closely related to the Ising and Potts models. I will describe a second uniqueness threshold on the wired regular tree, resolving a conjecture of Haggstrom from 1996, and explain how this threshold is tied to decay of correlations under wired boundary conditions. I will then discuss consequences for dynamics: near-optimal mixing of random-cluster Glauber dynamics on wired trees, and on random regular graphs in the low temperature uniqueness regime. These results give efficient sampling algorithms for the random-cluster and Potts models on treelike graphs. Based on joint work with A. Blanca, R. Gheissari, and H. Park.
Venue: MCS2068
Oct 12 13:00 Matthew Buckland: Polynomial Convergence of the Hamiltonian Monte Carlo algorithm for heavy-tailed distributions
Sampling methodologies based on the Hamiltonian Monte Carlo
(HMC) algorithm are used in state-of-the-art methodologies such as the
no-U-turns sampler (NUTS) in the platform Stan. HMC is also applied in
theoretical results to obtain improvements in comparison to standard
methodologies such as Random Walk Metropolis (RWM) as well as
Unadjusted Langevin Algorithm (ULA) or the Metropolis Adjusted Langevin
Algorithm (MALA). It has been established that HMC performs well for
light-tailed distributions, but any results for heavy-tailed
distributions are either not established or give at best polynomial
convergence upper bounds for the rate of convergence. In our recent
work we have produced asymptotically matching upper and lower bounds
polynomial convergence bounds for the HMC algorithm to a class of
heavy-tailed distributions. The lower bounds confirm that this
algorithm performs poorly for heavy-tailed distributions and provides
evidence that state-of-the-art samplers mentioned above, such as NUTS,
would also perform poorly when the target distribution has heavy tails.
In this talk we will go over the results and some of the proof
techniques.
Venue: MCS2068
Usual Venue: MCS3070
Contact: joe.thomas@durham.ac.uk
No upcoming seminars have been scheduled (not unusual outside term time).
