Nov 14 (Fri)
13:00 MCS0001 HEPMChristian Copetti (Oxford University): Symmetric Defects, families, anomalies and Quantum Hall systems
Defects are interesting probes which appear in a variety of contexts. Their interplay with bulk (generalized) symmetry gives rise to a rich landscape of representations. In this talk I will explain how interesting physical observables arise naturally from considering (topologically non-trivial) families of symmetric defects. A paramount example of this interplay are defects in theories with 't Hooft anomalies, such as (1+1) and (3+1)d chiral fermions. I will argue that the bulk anomalies imply interesting defect physics closely tied to the well known (fractional) quantum hall effect in two examples: boundary conditions and monodromy defects.
Venue: MCS0001
Nov 17 (Mon)
14:00 MCS3070 HEPJMario De Marco (U. Brussels): New 5d rank-one theories from discrete gauging
In recent years, it has been observed that the discrete-gauging of a 0-form symmetry leads to interesting physical phenomena (such as non-invertible symmetries), and can be used to generate new theories from old ones. In this talk, I will show how to apply this construction to the case of 5d N = 1 rank one SCFTs, leading to new exotic rank-one theories. As a byproduct, I will comment on the string and M-theory realization of 0-form symmetries, and of their discrete gauging.
Venue: MCS3070
14:00 MCS2068 PurePierre Will (Grenoble): Discrete groups in complex hyperbolic geometry
The complex hyperbolic space is a natural higher dimensional
generalisation of the classical
Poincaré disc. Its group of holomorphic isometries is \(PU(n,1)\), and
discrete subgroups of \(PU(n,1)\) provide
interesting actions on the complex hyperbolic space.
In this talk, I will first give a description of the complex hyperbolic
space, and explain some differences
with its real hyperbolic cousin. Then I will discuss simple examples of
discrete subgroups of \(PU(2,1)\) acting
on the complex hyperbolic plane, and try to present the questions that
are studied in the field (and some answers).
Venue: MCS2068
Nov 18 (Tue)
13:00 MCS2050 E&PSteven Bradley (Durham (Computer Science)): To Collect or To Collate: Data Sources for Pedagogical Research
13:00 MCS2068 APDEGonçalo Dos Reis (University of Edinburgh): Ito-Wentzell-Lions formula for conditional measure dependent random fields
We present several Itô-Wentzell formulae on Wiener spaces for real-valued functionals random field of Itô type depending on measures. We distinguish the full- and marginal-measure flow cases. Derivatives with respect to the measure components are understood in the sense of Lions.
Time allowing, we discuss additionally the Malliavin differentiability of McKean-Vlasov stochastic differential equations with common noise under the global Lipschitz assumption in the space variable and the measure variable. Our result gives meaning to the Malliavin derivative of the random probability measure that is the conditional law.
Venue: MCS2068
Nov 19 (Wed)
14:00 MCS2050 A&CHector Puerta Ramisa (Durham University): (Super) Conformal Weight Shifting Operators
Deriving (super) conformal blocks for correlators of generic multiplets is notoriously difficult. Weight-shifting operators offer an elegant construction of these blocks by acting on simpler, well understood seeds. In this talk, I will begin with a brief review of the (super)conformal bootstrap, then introduce the concept of weight-shifting operators and explain how to construct them for the general superconformal group SU(m,m|2n). As I will illustrate, these differential operators can act meaningfully on short multiplets (e.g. conserved currents in CFT or BPS superfields in SCFT), unlike previously known constructions. Furthermore, they provide the first systematic method to derive superconformal blocks of correlators of non-half-BPS supermultiplets in 4D N=2 and N=4. Based on 2506.08682.
Venue: MCS2050
Nov 20 (Thu)
13:00 MCS2068 G&TAmy Herron (University of Bristol): Triangle Presentations in ~A_2 Bruhat-Tits Buildings
The 1-skeleton of an ~A_2 Bruhat-Tits building is isomorphic to the Cayley graph of an abstract group with relations coming from triangle presentations. This abstract group either embeds into PGL(3, Fq((x))) or PGL(3, Qq), or else is exotic. Currently, the complete list of triangle presentations is only known for projective planes of orders q=2 or 3. However, one abstract group that embeds into PGL(3,Fq((x))) for any prime power q is known via the trace function corresponding to the finite field of order q^3. I found a new method to derive this group via perfect difference sets. This method demonstrates a previously unknown connection between difference sets and ~A_2 buildings. Moreover, this method makes the final computation of triangle presentations easier, which is computationally valuable for large q.
Venue: MCS2068
14:00 MCS2068 ProbPiNE (University of Edinburgh): No seminar PiNE in Edinburgh.
PiNE will take place in Edinburgh, see https://www.maths.dur.ac.uk/PiNE/25-11-20/index.html. Accordingly we will not have a seminar this week.
Venue: MCS2068
Nov 21 (Fri)
13:00 MCS0001 HEPMIda Zadeh (Southampton University): Asymmetric Orbifolds, Rank Reduction and Heterotic Islands
Exploring unknown regions of the moduli space of 2-dimensional conformal field theories plays an important role in understanding properties of theories of quantum gravity. In this talk I will discuss a family of world-sheet conformal field theories, asymmetric orbifolds, that describe some of these unexplored loci in the moduli space. I will focus on the application of asymmetric orbifolds to toroidal compactifications of heterotic string theory, and will consider theories in 6 and 4 dimensions with 16 supercharges and reduced rank. I will present a novel formalism, based on the Leech lattice, to construct islands without vector multiplets.
Venue: MCS0001
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Contact: arthur.lipstein@durham.ac.uk
Nov 19 14:00 Hector Puerta Ramisa (Durham University): (Super) Conformal Weight Shifting Operators
Deriving (super) conformal blocks for correlators of generic multiplets is notoriously difficult. Weight-shifting operators offer an elegant construction of these blocks by acting on simpler, well understood seeds. In this talk, I will begin with a brief review of the (super)conformal bootstrap, then introduce the concept of weight-shifting operators and explain how to construct them for the general superconformal group SU(m,m|2n). As I will illustrate, these differential operators can act meaningfully on short multiplets (e.g. conserved currents in CFT or BPS superfields in SCFT), unlike previously known constructions. Furthermore, they provide the first systematic method to derive superconformal blocks of correlators of non-half-BPS supermultiplets in 4D N=2 and N=4. Based on 2506.08682.
Venue: MCS2050
Usual Venue: MCS2068
Contact: yohance.a.osborne@durham.ac.uk
Nov 18 13:00 Gonçalo Dos Reis (University of Edinburgh): Ito-Wentzell-Lions formula for conditional measure dependent random fields
We present several Itô-Wentzell formulae on Wiener spaces for real-valued functionals random field of Itô type depending on measures. We distinguish the full- and marginal-measure flow cases. Derivatives with respect to the measure components are understood in the sense of Lions.
Time allowing, we discuss additionally the Malliavin differentiability of McKean-Vlasov stochastic differential equations with common noise under the global Lipschitz assumption in the space variable and the measure variable. Our result gives meaning to the Malliavin derivative of the random probability measure that is the conditional law.
Venue: MCS2068
Nov 25 13:00 Lukas Koch (University of Sussex): Uniform Lipschitz estimates for regularised optimal transport
I will discuss how to obtain Lipschitz estimates for regularised optimal transport problems using a variational approach. In particular, this gives Lipschitz regularity for entropic optimal transport independent of the regularisation parameter. A crucial step in the approach are local \(L^\infty\)-estimates, which are of independent interest. The talk is based on joint work with Rishabh Gvalani (ETH).
Venue: MCS2068
Dec 02 13:00 Estefania Loayza Romero (University of Strathclyde): TBC
Dec 09 13:00 Giacomo Borghi (Heriot-Watt University): TBC
Usual Venue: MCS3070
Contact: andrew.krause@durham.ac.uk
No upcoming seminars have been scheduled (not unusual outside term time).
Usual Venue: MCS2068
Contact: herbert.gangl@durham.ac.uk
Nov 25 14:00 Dante Luber (Queen Mary University of London): Matroid theory, algebra, and computation
Matroids combinatorially abstract independence properties of
finite dimensional linear algebra. They have become ubiquitous in
modern mathematics, and yield connections between graph theory,
algebra, polyhedral geometry, optimization, and beyond. Special
matroids capture the properties of point line arrangementments in
complex 2-projective space. The moduli space of all line arrangements
corresponding to a matroid is known as its realization space. After an
introduction to matroid theory, we will discuss how we have used the
OSCAR software system to study large datasets of matroids, isolating
examples whose realization spaces have interesting algebro-geometric
Venue: MCS2068
Dec 02 14:00 Jay Taylor (University of Manchester):
Dec 09 14:00 Fredrik Stromberg (University of Nottingham):
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
Nov 18 13:00 Steven Bradley (Durham (Computer Science)): To Collect or To Collate: Data Sources for Pedagogical Research
For staff moving into pedagogical research from other disciplines it can be difficult to know what "doing research" involves. Collecting primary data through questionnaires, interviews and focus groups is a common approach, but has challenges associated with ethical approval, familiarity with research design (e.g. writing questionnaires, facilitating focus groups), analysis (e.g. reflexive thematic analysis) and collection (particularly recruiting participants). I will talk about some of the data sources I have used in the papers I have written in computing education research, and how I have managed to publish without ever writing a questionnaire, conducting an interview or running a focus group - using existing data which is most likely available in every discipline.
Venue: MCS2050
Usual Venue: MCS2068
Contact: fernando.galaz-garcia@durham.ac.uk
Nov 20 13:00 Amy Herron (University of Bristol): Triangle Presentations in ~A_2 Bruhat-Tits Buildings
The 1-skeleton of an ~A_2 Bruhat-Tits building is isomorphic to the Cayley graph of an abstract group with relations coming from triangle presentations. This abstract group either embeds into PGL(3, Fq((x))) or PGL(3, Qq), or else is exotic. Currently, the complete list of triangle presentations is only known for projective planes of orders q=2 or 3. However, one abstract group that embeds into PGL(3,Fq((x))) for any prime power q is known via the trace function corresponding to the finite field of order q^3. I found a new method to derive this group via perfect difference sets. This method demonstrates a previously unknown connection between difference sets and ~A_2 buildings. Moreover, this method makes the final computation of triangle presentations easier, which is computationally valuable for large q.
Venue: MCS2068
Nov 27 13:00 Yan Rybalko (University of Oslo): Generic regularity of the two-component Novikov system
In my talk I will discuss the generic regularity of the Cauchy problem for the two-component Novikov system. This system is integrable (i.e., it is bi-Hamiltonian, has a Lax pair, and an infinite number of conservation laws), and admits peakon solutions of the form p(t)exp(-|x-q(t)|). Another important feature of the Novikov system is the wave-breaking phenomenon: the solutions remain bounded for all times, but the slope can blow-up in finite time. In our work, we show that there exists an open dense subset of C^k regular initial data, such that the corresponding global solutions persist the regularity for all t,x except, possibly, a finite number of piecewise C^{k-1} characteristic curves. Our approach builds on the work by Bressan and Chen, which relies on transforming solutions from Eulerian variables to a new set of Bressan-Constantin variables, in which all possible singularities of the original solutions are resolved. Then, applying the Thoms transversality theorem to the map related to the wave-breaking, we can construct an appropriate open dense subset of C^k regular initial data.
The talk is based upon the following papers:
K.H. Karlsen, Ya. Rybalko, "Generic regularity and a Lipschitz metric for the two-component Novikov system," in preparation.
K.H. Karlsen, Ya. Rybalko, "Global semigroup of conservative weak solutions of the two-component Novikov equation," Nonlinear Analysis: Real World Applications 86, 104393 (2025). DOI: 10.1016/j.nonrwa.2025.104393.
Venue: MCS2068
Jan 22 13:00 Chunyang Hu (Durham University): TBA
Mar 06 13:00 Julian Scheuer (Goethe University Frankfurt): TBA
Usual Venue: MCS3070
Contact: mendel.t.nguyen@durham.ac.uk
Nov 17 14:00 Mario De Marco (U. Brussels): New 5d rank-one theories from discrete gauging
In recent years, it has been observed that the discrete-gauging of a 0-form symmetry leads to interesting physical phenomena (such as non-invertible symmetries), and can be used to generate new theories from old ones. In this talk, I will show how to apply this construction to the case of 5d N = 1 rank one SCFTs, leading to new exotic rank-one theories. As a byproduct, I will comment on the string and M-theory realization of 0-form symmetries, and of their discrete gauging.
Venue: MCS3070
Usual Venue: MCS0001
Contact: p.e.dorey@durham.ac.uk,enrico.andriolo@durham.ac.uk,tobias.p.hansen@durham.ac.uk
Nov 14 13:00 Christian Copetti (Oxford University): Symmetric Defects, families, anomalies and Quantum Hall systems
Defects are interesting probes which appear in a variety of contexts. Their interplay with bulk (generalized) symmetry gives rise to a rich landscape of representations. In this talk I will explain how interesting physical observables arise naturally from considering (topologically non-trivial) families of symmetric defects. A paramount example of this interplay are defects in theories with 't Hooft anomalies, such as (1+1) and (3+1)d chiral fermions. I will argue that the bulk anomalies imply interesting defect physics closely tied to the well known (fractional) quantum hall effect in two examples: boundary conditions and monodromy defects.
Venue: MCS0001
Nov 21 13:00 Ida Zadeh (Southampton University): Asymmetric Orbifolds, Rank Reduction and Heterotic Islands
Exploring unknown regions of the moduli space of 2-dimensional conformal field theories plays an important role in understanding properties of theories of quantum gravity. In this talk I will discuss a family of world-sheet conformal field theories, asymmetric orbifolds, that describe some of these unexplored loci in the moduli space. I will focus on the application of asymmetric orbifolds to toroidal compactifications of heterotic string theory, and will consider theories in 6 and 4 dimensions with 16 supercharges and reduced rank. I will present a novel formalism, based on the Leech lattice, to construct islands without vector multiplets.
Venue: MCS0001
Nov 28 13:00 Tim Meier (Santiago de Compostela): TBA
Dec 05 13:00 Marco Meineri (Torino University): The Numerical Bootstrap of Points and Lines
I will describe how to constrain the conformal field theory data attached to boundary conditions of two dimensional theories, using the numerical bootstrap. Even for rational theories, it is hard to construct examples of boundary conditions which break all symmetry except Virasoro, let alone classify them. Yet, as always, the OPE data associated with each conformal boundary condition obeys crossing and unitarity. The ensuing constraints can be organized in a semidefinite program, which allows exploration of a multi-dimensional parameter space involving bulk and boundary data.
Venue: MCS0001
Dec 12 13:00 Sungwoo Hong (KAIST, Taejon): TBA
Usual Venue: MCS2068
Contact: tyler.helmuth@durham.ac.uk,oliver.kelsey-tough@durham.ac.uk
Nov 20 14:00 PiNE (University of Edinburgh): No seminar PiNE in Edinburgh.
PiNE will take place in Edinburgh, see https://www.maths.dur.ac.uk/PiNE/25-11-20/index.html. Accordingly we will not have a seminar this week.
Venue: MCS2068
Nov 27 14:00 Omer Angel (University of British Columbia): min/max trees
On a regular tree, assign each vertex a random independent value. Two players alternate choosing a child of the current vertex. When reaching level n, player 1 pays player 2 the cumulative sum of the values along the chosen path. We show that in certain cases the value of this game converges as n\to\infty, and discuss the challenges in extending our results. Joint with Gourab Ray and Yinon Spinka.
Venue: MCS2068
Dec 04 14:00 Kohei Suzuki (Department of Mathematics, Durham University): Interacting Brownian Motions, Wasserstein Gradient Flow and Ricci Curvature
In this talk, we focus on an infinite-dimensional model of interacting Brownian motions: Dyson Brownian motion at soft-edge scaling. Its stationary process is the Airy line ensemble, a central object in KPZ universality. We show that its time-marginal law forms a Wasserstein gradient flow of the relative entropy in the space of probability measures over the infinite-dimensional configuration space an infinite-dimensional analogue of Jordan-Kinderlehrer-Otto theory. This yields an optimal transport-first construction of the model, bridging Airy line ensemble/KPZ and optimal transport. From a metric-geometric viewpoint, our result shows that the configuration space endowed with the Airy_2 point process is an RCD space, a space having a uniform lower Ricci curvature bound in the sense of Lott-Villani/Sturm. As an application, (a) we establish various new functional inequalities (e.g., HWI, Brunn-Minkowski, dimension-free Harnack) for the model; (b) we discover a new propagation-of-rigidity phenomenon: the time-marginal law exhibits number rigidity in the sense of Ghosh and Peres, revealing a formation of a random crystal by long-range repulsively interacting Brownian motions. This talk is based on arXiv:2509.06869<https://arxiv.org/abs/2509.06869>.
Venue: MCS2068
Usual Venue: MCS2068
Contact: michael.r.magee@durham.ac.uk
Nov 17 14:00 Pierre Will (Grenoble): Discrete groups in complex hyperbolic geometry
The complex hyperbolic space is a natural higher dimensional
generalisation of the classical
Poincaré disc. Its group of holomorphic isometries is \(PU(n,1)\), and
discrete subgroups of \(PU(n,1)\) provide
interesting actions on the complex hyperbolic space.
In this talk, I will first give a description of the complex hyperbolic
space, and explain some differences
with its real hyperbolic cousin. Then I will discuss simple examples of
discrete subgroups of \(PU(2,1)\) acting
on the complex hyperbolic plane, and try to present the questions that
are studied in the field (and some answers).
Venue: MCS2068
Dec 01 14:00 Brian Petri (Jussieu): TBA
Dec 08 14:00 Stuart White (Oxford): TBA
Usual Venue: MCS3070
Contact: joe.thomas@durham.ac.uk
No upcoming seminars have been scheduled (not unusual outside term time).
