Nom de l'auteur
Cardoen
Prénom de l'auteur
Clément
Date de soutenance
Nom du ou des directeurs de thèse
Nouy

The objective of this thesis is to solve non-linear hyperbolic conservation laws by measure-based approaches. The first contribution is a numerical method to solve parameter-dependent scalar hyperbolic partial differential equations (PDEs) with a moment approach, based on a previous work from Marx et al. (2020). This approach relies on a very weak notion of solution of nonlinear equations, namely parametric entropy measure-valued (MV) solutions. The infinite-dimensional linear problem is approximated by a hierarchy of convex, finite-dimensional, semidefinite programming problems, called Lasserre's hierarchy. Finally, several post-treatments can be performed, including reconstructing the graph of the solution. The second contribution is a model order reduction method to solve scalar hyperbolic PDEs with a moment approach, inspired of a previous work from Ehrlacher et al. (2020). In this method, we see the snapshots as measures linked to the solutions, and define the approximation space as the set of Wasserstein barycenters of these snapshots. The offline and online phases are then based on a projection onto the approximation space, which is obtained through an optimization phase which consists in minimizing deviation from some moment information on the solution.

Etablissement d'origine
Ecole Centrale de Nantes

comment

type actualité

Soutenance de thèse de Clément Cardoen, jeudi 18 décembre, 14h, salle 3

Date de début de l'actualité
18-12-2025 14:00
Date de fin de l'actualité
18-12-2025 17:00

J'ai le plaisir de vous convier à ma soutenance de thèse intitulée

Measure-based Approaches for Model Order Reduction

The objective of this thesis is to solve non-linear hyperbolic conservation laws by measure-based approaches. The first contribution is a numerical method to solve parameter-dependent scalar hyperbolic partial differential equations (PDEs) with a moment approach, based on a previous work from Marx et al. (2020). This approach relies on a very weak notion of solution of nonlinear equations, namely parametric entropy measure-valued (MV) solutions. The infinite-dimensional linear problem is approximated by a hierarchy of convex, finite-dimensional, semidefinite programming problems, called Lasserre's hierarchy. Finally, several post-treatments can be performed, including reconstructing the graph of the solution. The second contribution is a model order reduction method to solve scalar hyperbolic PDEs with a moment approach, inspired of a previous work from Ehrlacher et al. (2020). In this method, we see the snapshots as measures linked to the solutions, and define the approximation space as the set of Wasserstein barycenters of these snapshots. The offline and online phases are then based on a projection onto the approximation space, which is obtained through an optimization phase which consists in minimizing deviation from some moment information on the solution.

William Hide
Etablissement de l'orateur
Oxford
Date et heure de l'exposé
Lieu de l'exposé
salle des séminaires
Résumé de l'exposé

Based on joint work with Davide Macera and Joe Thomas. The first non-zero eigenvalue, or spectral gap, of the Laplacian on a closed hyperbolic surface encodes important geometric and dynamical information about the surface. We study the size of the spectral gap for random large genus hyperbolic surfaces sampled according to the Weil-Petersson probability measure. We show that there is a c>0 such that a random surface of genus g has spectral gap at least 1/4-O(g^-c) with high probability. Our approach adapts the polynomial method for the strong convergence of random matrices, introduced by Chen, Garza-Vargas, Tropp and van Handel, and its generalization to the strong convergence of surface groups by Magee, Puder and van Handel, to the Laplacian on Weil-Petersson random hyperbolic surfaces.

Baptiste Serraille
Etablissement de l'orateur
ETH Zurich
Date et heure de l'exposé
Lieu de l'exposé
Résumé de l'exposé
Irene SILVESTRE-ROSELLÓ
Etablissement de l'orateur
Université de Montréal (UdeM)
Date et heure de l'exposé
Lieu de l'exposé
Salle Eole
Résumé de l'exposé

Dans la nature (et dans les mathématiques) se trouvent des fonctions qui oscillent beaucoup. Mais, quelle est la façon la plus efficace de les étudier? La réponse de la topologie persistante est «ignorez les petites oscillations». Dans cet exposé nous introduirons les modules de persistance (ou codes-barres), un concept de la topologie persistante, et expliquerons comment les utiliser pour comparer des fonctions sur des variétés riemanniennes compactes. Après, nous appliquerons cet outil pour compter grossièrement les domaines nodaux des combinaisons linéaires de fonctions propres de certains opérateurs.

Contact
Elise Goujard
Contact E-mail
elise.goujard@univ-nantes.fr
date de fin du contrat
Dénomination
IUF
Equipe
Contact
Erwan Brugallé
Contact E-mail
erwan.brugalle@univ-nantes.fr
date de fin du contrat
Dénomination
Europe Staff Exchange MAGA
Equipe
Contact
Marco Golla
Contact E-mail
marco.golla@univ-nantes.fr
date de fin du contrat
Dénomination
Europe Top-SCoLDS
Equipe
Contact
Vincent Colin
Contact E-mail
vincent.colin@univ-nantes.fr
date de fin du contrat
Dénomination
IUF
Equipe
Contact
Guillaume Poly
Contact E-mail
guillaume.poly@univ-nantes.fr
date de fin du contrat
Dénomination
ANR Lessbig
Equipe