Exposé

Procédure Bootstrap pour tester la nullité des composantes de la variance dans les modèles à effets mixtes

Jeudi, 16 octobre 2025 - 10:15 - 11:15
Résumé: Nous examinons le problème du test des composantes de variance dans les modèles à effets mixtes à l’aide du test du rapport de vraisemblance. Nous tenons compte de la présence de paramètres de nuisance, c’est-à-dire du fait que certaines variances non testées peuvent également être nulles. Deux difficultés principales se présentent dans ce contexte. Premièrement, sous l’hypothèse nulle, la vraie valeur du paramètre se trouve sur la frontière de l’espace des paramètres.

Finite-sample statistical guarantees for learning dynamical systems in state-space form

Jeudi, 27 novembre 2025 - 10:15 - 11:15

In this talk, I will present an overview of recent results on finite-sample Probably Approximately Correct (PAC) and PAC-Bayesian bounds for learning partially observed dynamical systems in state-space form. For clarity, we begin with linear stochastic systems in discrete time, learned from a single trajectory, and then discuss extensions to more complex nonlinear settings.

On the derivation of mean-curvature flow and its fluctuations from microscopic interactions

On the derivation of mean-curvature flow and its fluctuations from microscopic interactions

Jeudi, 11 septembre 2025 - 11:30 - 12:30

The emergence of mean-curvature flow of an interface between different phases or populations is a phenomenon of long standing interest in statistical physics.  
In this talk, we review recent progress with respect to a class of reaction-diffusion stochastic particle systems on an $n$-dimensional lattice.
In such a process, particles can move across sites as well as be created/annihilated according to diffusion and reaction rates.  
These rates will be chosen so that there are two preferred particle mass density levels $a_1$, $a_2$ in `balance'.

Optimal inference for the mean of random functions

Jeudi, 2 octobre 2025 - 10:15 - 11:15

We study estimation and inference for the mean of real-valued random func- tions defined on a hypercube. The independent random functions are observed on a discrete, random subset of design points, possibly with heteroscedastic noise. We propose a novel optimal-rate estimator based on Fourier series expansions and establish a sharp non-asymptotic error bound in L2−norm.

Local and nonlocal density estimates for variational problems with degenerate double-well potentials

Mardi, 14 octobre 2025 - 11:30 - 12:30

In this seminar we present some recent results regarding density estimates for level sets of minimizers of local and nonlocal energies, which arise from phase separation problems, such as the Ginzburg-Landau energy functional. In particular, we prove density estimates when the phase separation is induced by a double-well potential which presents a slow growth from the pure phases. As a byproduct, we obtain the uniform convergence of the interfaces of any sequence of minimizers of a suitably rescaled energy functional to a set with Hausdorff codimension one.

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