Séminaire: Problèmes Spectraux en Physique Mathématique


Année 2025-2026



Pour tout renseignement complémentaire, veuillez contacter les organisateurs, Hakim Boumaza, Mathieu Lewin ou Stéphane Nonnenmacher.

Prochain séminaire le lundi 15 décembre 2025 après-midi à l'Institut Henri Poincaré, en salle Pierre Grisvard (3e étage, ex-314)


14h - 15h Gabriel Rivière (Nantes) Nonlinear chaotic Vlasov equations.

Abstract:

I will present a joint work with Yann Chaubet and Daniel Han-Kwan (Nantes). I will discuss the long time behaviour of the nonlinear Vlasov equation set on a negatively curved manifold when the interaction kernel is smooth. I will explain that, for small initial data supported away from the zero section, solutions to this equation converge exponentially fast to an equilibrium state of the linear problem. The proof of this result relies on tools from microlocal analysis initially developed in the context of hyperbolic dynamical systems.
  15h15 - 16h15 Eric Cancès (ENPC)
Quantum Hamiltonians for twisted bilayer graphene: construction and spectral properties

Abstract:

The engineering of multilayer two-dimensional and moiré materials with tailored electronic, optical, and mechanical properties has become a central theme in contemporary condensed matter physics and materials science. In this talk, I will discuss the construction and spectral analysis of quantum Hamiltonians modeling the electronic structure of one of the most prominent moiré materials: twisted bilayer graphene. In the periodic setting (untwisted bilayer graphene and twisted bilayer graphene with a rational twist parameter), first-principles Density Functional Theory models yield mean-field Hamiltonians whose spectral properties can be described in detail using Bloch theory. In the aperiodic case (irrational twist parameter), one can still build approximate mean-field Hamiltonians and study their spectra by either embedding the problem into a higher dimensional periodic framework or by using the C-algebra approach pioneered by Bellissard and collaborators. The small angle regime is of particular interest, as twisted bilayer graphene exhibits unconventional superconductivity near the so-called magic angle θ ≈ 1.1° ; this limit can be analyzed using semiclassical techniques. I will present recent and ongoing work with several collaborators (Louis Garrigue, David Gontier; Daniel Massatt, Long Meng, Etienne Polack, Xue Quan; Francis Nier), and put these results into perspective.


Prochaines séances :

5 janvier 2026: Jean-Marc Bouclet, Zhongkai Tao
9 février 2026: Alvise Bastianello
13 avril 2026
11 mai 2026
15 juin 2026

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Dernière mise à jour: 8 décembre 2025
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