In and out of lockdown: Propagation of supply and demand shocks in a dynamic input-output model
Pichler, A Pangallo, M del Rio-Chanona, R Lafond, F Farmer, J (18 Feb 2021)
The unequal effects of the health-economy tradeoff during the COVID-19 pandemic
Pangallo, M Aleta, A Chanona, R Pichler, A Martín-Corral, D Chinazzi, M Lafond, F Ajelli, M Moro, E Moreno, Y Vespignani, A Farmer, J (07 Dec 2022)
Tue, 04 Feb 2025
15:30
L4

Global logarithmic deformation theory

Simon Felten
(Oxford)
Abstract

A well-known problem in algebraic geometry is to construct smooth projective Calabi-Yau varieties $Y$. In the smoothing approach, we construct first a degenerate (reducible) Calabi-Yau scheme $V$ by gluing pieces. Then we aim to find a family $f\colon X \to C$ with special fiber $X_0 = f^{-1}(0) \cong V$ and smooth general fiber $X_t = f^{-1}(t)$. In this talk, we see how infinitesimal logarithmic deformation theory solves the second step of this approach: the construction of a family out of a degenerate fiber $V$. This is achieved via the logarithmic Bogomolov-Tian-Todorov theorem as well as its variant for pairs of a log Calabi-Yau space $f_0\colon X_0 \to S_0$ and a line bundle $\mathcal{L}_0$ on $X_0$.

Wed, 07 May 2025
16:00
L3

Drawing Knots on Surfaces

Samuel Ketchell
(University of Oxford)
Abstract

There is a well-known class of knots, called torus knots, which are those that can be drawn on a "standardly embedded" torus (one that separates the 3-sphere into two solid tori). A fairly natural property of other knots to consider is the genus necessary for that knot to be drawn on a standardly embedded genus g surface. This knot invariant has been studied under the name "embeddability". The goal of this talk is to introduce the invariant, look at some upper and lower bounds in terms of other invariants, and examine its behavior under connected sum.

Wed, 05 Mar 2025
16:00
L6

The BNSR Invariant of an Artin group and graph colorings.

Marcos Escartin-Ferrer
(Universidad Zaragoza)
Abstract

The BNSR Invariant is a classical geometric invariant that encodes the finite generation of all coabelian subgroups of a given finitely generated group. The aim of this talk is to present a conjecture about the structure of the BNSR invariant of an Artin group and to present a new family in which the conjecture is true in terms of graph colorings.

Wed, 26 Feb 2025
16:00
L6

Ultrasolid Modules and Deformation Theory

Sofía Marlasca Aparicio
(University of Oxford)
Abstract

We introduce ultrasolid modules, a variant of complete topological vector spaces. In this setting, we will prove some results in commutative algebra and apply them to the deformation of algebraic varieties in the language of derived algebraic geometry.

Tue, 04 Feb 2025
13:00
L5

Symmetries of Coupled Minimal Models

Connor Behan
(ITP Sao Paolo)
Abstract

When tensor products of N minimal models accumulate at central charge N, they also admit relevant operators arbitrarily close to marginality. This raises the tantalizing possibility that they can be use to reach purely Virasoro symmetric CFTs where the breaking of extended chiral symmetry can be seen in a controlled way. This talk will give an overview of the theories where this appears to be the case, according to a brute force check at low lying spins. We will also encounter an interesting non-example where the same type of analysis can be used to give a simpler proof of integrability.

Tue, 11 Mar 2025
15:30
L4

Quiver with potential and attractor invariants

Pierre Descombes
(Imperial College London)
Abstract
Given a quiver (a directed graph) with a potential (a linear combination of cycles), one can study moduli spaces of the associated noncommutative algebra and associate so-called BPS invariants to them. These are interesting because they have a deep link with cluster algebras and provide some kind of noncommutative analogue of DT theory, the study of sheaves on Calabi-Yau 3-folds.
The generating series of BPS invariants for interesting quivers with potentials are in general very wild. However, using the Kontsevich-Soibelman wall-crossing formula, a recursive formula expresses the BPS invariants in terms of so-called attractor invariants, which are expected to be simple in interesting situations. We will discuss them for quivers with potential associated to triangulations of surfaces and quivers with potential giving noncommutative resolutions of CY3 singularities.
Tue, 11 Mar 2025
16:00
L6

On non-Gaussian multiplicative chaos

Mo Dick Wong
(Durham University)
Abstract

We consider two approximation schemes for the construction of a class of non-Gaussian multiplicative chaos, and show that they give rise to the same limit in the entire subcritical regime. Our approach uses a modified second moment method with the help of a new coupling argument, and does not rely on any Gaussian approximation or thick point analysis. As an application, we extend the martingale central limit theorem for partial sums of random multiplicative functions to L^1 twists. This is a joint work with Ofir Gorodetsky.

Tue, 04 Mar 2025
16:00
L6

Fermionic structure in the Abelian sandpile and the uniform spanning tree

Alessandra Cipriani
(University College London)
Abstract
In this talk we consider a stochastic system of sand grains moving on a finite graph: the Abelian sandpile, a prototype of self-organized lattice model. We focus on the function that indicates whether a single grain of sand is present at a site, and explore its connections with the discrete Gaussian free field, the uniform spanning tree, and the fermionic Gaussian free field. Based on joint works with L. Chiarini (Durham), R. S. Hazra (Leiden), A. Rapoport and W. Ruszel (Utrecht).



 

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