Universality of fully parked trees and catalytic equations.

• Nicolas Curien (LMO, Université Paris-Saclay)

Room: small amphitheater We show that critical parking trees conditioned to be fully parked converge in the scaling limits towards the Brownian growth-fragmentation tree, a self-similar Markov tree different from Aldous’ Brownian tree. As a by-product of our study, we prove that positive non-linear functional equations involving a catalytic variable display a universal polynomial exponent 5/2 at their singularity, confirming a conjecture by Chapuy, Schaeffer and Drmota & Hainzl. Compared to previous analytical works on the subject, our approach is probabilistic and exploits an underlying random walk hidden in the random tree model. Joint work with Alice Contat.

Counting Calabi-Yau black holes with mock modular forms

• Boris Pioline (LPTHE, Sorbonne Université)

Room: small Amphitheater Once put into suitable generating series, various enumerative invariants on Calabi-Yau threefolds are expected to possess modular properties, allowing to determine them uniquely from a few data points and giving powerful control on their asymptotic growth. This includes Gromov-Witten invariants in presence of a genus one fibration, Noether-Lefschetz invariants in presence of a K3 fibration, as well as Donalson-Thomas invariants supported on divisors (without requiring any particular fibration). While modularity has a clear mathematical origin in the first two cases, it is more mysterious in the last case, corresponding physically to BPS indices counting D4-D2-D0 black holes. I will review recent progress in testing the modularity (or more generally mock modularity) of D4-D2-D0 indices in one-parameter Calabi-Yau threefolds such as the quintic threefold, and in leveraging these results to compute Gopakumar-Vafa invariants at higher genus than hitherto possible. Based on work in collaboration with Sergey Alexandrov, Soheyla Feyzbakhsh, Albrecht Klemm and Thorsten Schimannek

Entanglement and renormalisation of spin systems in the generalised Landau paradigm

• Clément Delcamp (IHÉS)

Room: small Amphitheater Invoking results from topological quantum field theory, I will demonstrate that for every spin system representing a symmetric gapped phase, one can find a dual physical system whose dual symmetry is spontaneously broken. I will argue that this result has strong implications for the classical simulation of spin systems using variational tensor network methods, as this dual physical system minimises both the entanglement entropy and the required number of variational parameters. The applicability of this method will be demonstrated by introducing a generalised Density Matrix Renormalisation Group algorithm.

Theorems for the modular and lightcone bootstrap

• Balt Van Rees (CPHT, École Polytechnique)

Room: small Amphitheater We consider the implications of modular invariance for the spectrum of two-dimensional CFTs. For states with high energy this question was analyzed at a qualitative level by Cardy in 1986, but rigorous statements were almost entirely absent until the analysis (based on Tauberian theorems) by Mukhametzhanov and Zhiboedeov in 2019. In this talk we consider states with a very large spin, for which we show that it is possible to obtain much stronger rigorous results. Using complex analysis we in particular demonstrate that the spectrum of twists necessarily becomes dense for every large spin. We analyze the size of the subleading corrections, which will allow us to estimate how rapidly the maximal spacing between operators goes to zero. An entirely analogous procedure can be applied to four-point functions of identical operators in CFTs with a twist gap. Talk based on work in progress with Sridip Pal and Jiaxin Qiao.

What can the gluing equation matrices tell us about a 3-manifold?

• Stavros Garoufalidis (ICM-SUSTech, and IHÉS)

Room: small Amphitheater Ideal triangulations of 3-manifolds with nonempty boundary were introduced by Thurston as an effective means of computing the complete hyperbolic structure on a cusped hyperbolic 3-manifold and its Dehn fillings. The combinatorics of the triangulations leads to gluing equations via Neumann-Zagier matrices, and these in turn lead to a plethora of quantum 3-manifold invariants. We will give a sample of such invariants that include the 3D-index, the Kashaev-Luo-Vartanov state integrals the quantum dilogarithm invariants of G.-Kashaev and the perturbative Chern-Simons invariants around q=1 of G.-Wheeler-Storzer.