Séminaire Matrices et graphes aléatoires (MEGA)

Les thèmes abordés incluent

Dates 2026-2027

Pour l'année universitaire 2026-2027, le séminaire MEGA aura lieu aux dates suivantes: 09/10/2026, 13/11/2026, 11/12/2026 (à l'école Polytechnique), 15/01/2027, ?/02/2027 (à Toulouse), 12/03/2027, 30/04/2027, 21/05/2027 et 25/06/2027

Prochaine séance

Vendredi 9 Octobre, à l'IHP.

Abstract: In this lecture I will point at some recent developments in non-Hermitian random matrix theory. The symmetry classification of Bernard and Le Clair from the late 90's has been recently revisited by Kawabata et al., finding a total of 38 classes. Short after, based on numerics and heuristic arguments it was conjectured by Hamazaki et al. that in the limit of large matrices only three generic statistics exist in the bulk of the spectrum. The simplest representatives are given by complex symmetric, complex self-dual and complex Ginibre matrices, called class A, AI$^\dagger$ and AII$^\dagger$. Starting from class A which represents a determinantal point process, I will explain the relation between characteristic polynomials and planar orthogonal polynomials. Being unavailable for the latter two classes, different techniques apply and I will briefly summarise some very recent results based on the Kac-Rice formalism and replicas. A more probabilistic approach is currently open.

Abstract:The derivatives of a determinant or Pfaffian divided by a Vandermonde determinant occur in the study of characteristic polynomials for random matrix ensembles with unitary (determinantal) or orthogonal or symplectic (Pfaffian) structure. For the unitary case, the expansions in terms of determinants with derivative numbers varying according to row or column, have a relatively simple expression in terms of Kostka numbers. For the orthogonal and symplectic cases, the expansion in Pfaffians leads to more complex coefficients, as shown in collaborative work with Gernot Akemann, Mario Kieburg and Adrian Padellaro. Here we show the non-negativity of the coefficients used in this expansion by providing a combinatorial interpretation. We translate binomial coefficients to lattice path counts, and show non-negativity by a generalisation of the Lindstr\“om–Gessel–Viennot lemma.

This is joint work with Adrian Padellaro in preparation.

Abstract: It has been conjectured that generic spectral statistic in the bulk and at the edge in all 38 symmetry classes of non-Hermitian random matrix theory follows a threefold way. The simplest symmetry classes that display these limiting universality classes are Gaussian complex symmetric, complex self-dual and complex Ginibre random matrices. In the Cartan classification these are labelled as class A, AI$^\dagger$ and AII$^\dagger$, respectively. Despite recent progress it remains difficult to obtain general multi-point density correlation functions in the latter two classes. Here, we will consider expectation values of products of pairs of complex conjugated characteristic polynomials as observables in these three ensembles, including their elliptic deformation. Explicit results will be presented for finite matrix size $N$ and in the large-$N$ limit.

Année 2026-2027

* Organisateurs 2026-2027.

* Vendredi 9 octobre, à l'IHP

* Vendredi 13 Novembre, à l'IHP

* Vendredi 11 Décembre, à l'Ecole Polytechnique

* Vendredi 15 Janvier, à l'IHP

* Vendredi ?? Février, à Toulouse

* Vendredi 12 Mars, à l'IHP

* Vendredi 30 Avril, à l'IHP

* Vendredi 21 Mai, à l'IHP

* Vendredi 25 Juin, à l'IHP

Année 2025-2026

* Organisateurs 2025-2026.

* Vendredi 10 octobre, à l'IHP

* Vendredi 21 novembre, à l'IHP

* Vendredi 5 décembre, au CMLS à l'Ecole Polytechnique

* Vendredi 16 janvier, à l'IHP

* Vendredi 20 février, à Toulouse

* Vendredi 13 mars, à l'IHP

* Vendredi 10 avril, à l'IHP

* Vendredi 29 mai, Journée commune MEGA & IASIS** à l'IHP

* Vendredi 26 juin, à l'Ecole polytechnique

Année 2024-2025

Année 2023-2024

Année 2022-2023

Année 2021-2022

Année 2020-2021

Année 2019-2020

Année 2018-2019

Année 2017-2018

Année 2016-2017

Année 2015-2016

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Année 2014-2015

Histoire

Le séminaire MEGA a été créé en 2014 par Djalil Chafaï et Camille Male avec l'aide de Florent Benaych-Georges.

Image est tirée de https://www.mat.tuhh.de/forschung/aa/forschung.html.