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CIRM – Centre International de Rencontres Mathématiques

The research school is an introductory meeting to the thematic program “Representation Theory and Noncommutative Geometry” to be held at IHP from January to March 2025. The trimester is part of an ongoing effort to bridge two fiels of Mathematics : the representation theory of locally compact groups and the theory of operator algebras. These research domains share origins in harmonic analysis, spectral theory and quantum mechanics but grew in separate directions. Recent progress in representation theory, involving especially non-Riemannian symmetric spaces and spherical varieties, and new tools developed in operator algebras, especially those involving K-theory and the other methods of non-commutative geometry, offer exciting prospects for new work at the interface between the two fields.

CIRM – Centre International de Rencontres Mathématiques

The main goal of these Etats de la recherche is to review some of the most recent spectacular developments in algebraic, analytic and arithmetic dynamics. Covered themes will include a variety of problems related to the iteration of rational maps on algebraic varieties as well as the study of their dynamical moduli spaces. Depending on the structure of the ambient field over which these maps are defined, methods may vary drastically. Over the field of complex numbers, one speaks of holomorphic dynamics in which quasi-conformal deformations play a key role. The case of maps defined over general metrized fields have led to the developments of dynamics over Berkovich spaces. One can also consider maps over number fields whose study lies at the core of arithmetic dynamics. Interactions between these various fields have deepened in the recent years. Complex pluripotential theory combined with tools from arithmetic geometry has been used to prove equidistribution results with applications to problems of unlikely intersection, and to explore dynamical moduli spaces and their special varieties. Methods in p-adic analysis and from the minimal model program have revolutionized our understanding of groups of birational transformations. Non-archimedean dynamics has been turned into a very efficient tool to analyze degeneration problems in holomorphic dynamics.

Algèbre,    Analyse

CIRM – Centre International de Rencontres Mathématiques

Solving time-harmonic wave equations with iterative methods is very challenging because they combine multiple difficulties like e.g. highly oscillatory solutions and complex non-Hermitian and indefinite discrete operators. In addition, the wave number associated to the numerical solution is different from the one of the exact solution thus leading to so-called numerical dispersion which requires very fine mesh to be controlled. There exists numerical schemes designed to reduce the dispersion error where the most used technique to build them relies on stencils involving free parameters that are next obtained by numerically minimizing the dispersion error. In the past few years, we develop an alternative approach called asymptotic dispersion correction. The latter is based on the introduction of a perturbation of the wavenumber (the shift) in the numerical scheme. We then explicitly compute the shift that minimizes the dispersion error for small enough meshsize. In addition, we show that our method can be applied to any finite difference scheme and reduces the relative error. We emphasize that most of works dealing with dispersion reducing methods consider the Helmholtz equation. The goal of the Research in Residence is to extend the asymptotic dispersion correction to the convected Helmholtz equation that can be used to model time-harmonic wave propagation in a moving flow.

Analyse,    Calcul infinitésimal, équations différentielles et intégrales

CIRM – Centre International de Rencontres Mathématiques

This Thematic Month aims to cover topics related to singularity theory of algebraic or analytic spaces, algebraic study of differential equations, and their applications to questions of transcendence. This 5-week program covers different themes that are often not closely related. One of the main objectives is to make them interact. To encourage participants (especially the youngest ones) to attend the entire month and foster interactions outside each one’s expertise zone, the scientific program of each week of the month will consist of courses accessible to non-experts, as well as more specialized presentations.

CIRM – Centre International de Rencontres Mathématiques

K-stability is a central topic in modern complex geometry. It characterises Fano manifolds that admit a Kähler-Einstein metric and provides a good notion of compact moduli space for Fano varieties. The winter school will bring together experts on K-stability who will give 8 mini-courses for PhD students and young researchers with a special focus on explicit problems in dimensions two and three. Along with lecture courses, there will be exercise sessions.

CIRM – Centre International de Rencontres Mathématiques

We plan to work on several explicit problems about K-stability of smooth and singular Fano threefolds described in the proposal together with Hamid Abban (Nottingham, England) and Kento Fujita (Osaka, Japan). Hamid Abban works on K-stability of Fano varieites, and birational geometry of Fano varieties. His recent results on K-stability crucially changed the subject over the last two years. Kento Fujita is an expert in the general theory of K-stability of Fano varieties. One of the most important works of Fujita consisted on finding and proving a valuative criterion for K-stability.

CIRM – Centre International de Rencontres Mathématiques

The school will introduce participants to several hot research topics at the frontier between geophysical fluid dynamics, fundamental physics and mathematics. The main themes will be spontaneous stochasticity, waves in geophysical and astrophysical fluids and fundamental challenges in hydrodynamic and wave turbulence. The school will consist of several lecture series, plus a number of research seminars, covering mathematical, theoretical and experimental aspects. The school is organized in the framework of an international collaboration which started in 2019 and which is financially supported by the Simons Foundation (https://cims.nyu.edu/wave-turbulence/people/). This “Simons Collaboration on Wave Turbulence” brings together physicists and mathematicians with the aim of addressing fundamental questions about the Wave Turbulence theory and its applicability to real systems and especially to the Earth climate system.

Mathématiques appliquées (en général),    Physique numérique

CIRM – Centre International de Rencontres Mathématiques

The interactions between dynamics and geometry in dimensions up to three are fertile, they have been at the origin of many recent discoveries. A particularly nice example is the genericity of the set of three-dimensional Reeb flows admitting infinitely many periodic orbits. These interactions are also at the heart of a number of current research programs around the world in various directions. Transverse geometric structures (possibly singular), for example, represent a promising line of work for the study of Anosov flows in dimension three. Methods and concepts from one-dimensional dynamical systems, singular geometric structures on surfaces (of which translation surfaces are the paradigmatic example) and three-dimensional flows are fundamental. These ideas permeate a large part of mathematics, inspiring many higherdimensional notions, but are not as well-known as they should be by a wider public of young researchers in geometry and dynamics. The aim of this summer school is to help filling this gap, through three in-depth mini-courses on circle diffeomorphisms, translation surfaces and the dynamics of three-dimensional Reeb flows.