[Dottorcomp] Fwd: Aujourd'hui vendredi 31 mars à 14h au Séminaire du LJLL : Muhammad Hassan (exposé avec diffusion simultanée par Zoom)

[Lorenzo Tamellini]

Buongiorno,

ricevo e inoltro l'avviso di seminario qui sotto

Cordiali saluti,
Lorenzo Tamellini

---------- Forwarded message ---------
Da: Seminaire du Laboratoire Jacques-Louis Lions <
Seminaire-du-LJLL a ann.jussieu.fr>
Date: ven 31 mar 2023 alle ore 02:49
Subject: Aujourd'hui vendredi 31 mars à 14h au Séminaire du LJLL : Muhammad
Hassan (exposé avec diffusion simultanée par Zoom)
To:


*Aujourd'hui vendredi 31 mars 2023 à 14h au Séminaire du Laboratoire
Jacques-Louis Lions *

*Muhammad Hassan* (Sorbonne Université, Paris)

*Quantitative error estimates for the single-reference coupled cluster
method in quantum computational chemistry*

*Résumé*
Coupled cluster methods are widely regarded as among the most effective
algorithms for high precision resolution of the ground state energy of the
electronic Schrödinger equation in the dynamical correlation regime.
Despite their ubiquitous usage as “gold-standard” methods in quantum
computational chemistry, the numerical analysis of the coupled cluster
methodology is underdeveloped. The existing numerical analysis relies on a
{local strong monotonicity} property of the coupled cluster function that
is valid only in a perturbative regime, i.e., when the sought-after coupled
cluster solutions are sufficiently close to zero. In particular,
quantitative error estimates for coupled cluster methods in practical
situations largely do not exist.
The goal of this talk is to present a new well-posedness analysis for the
{single-reference} coupled cluster method based on the invertibility of the
coupled cluster Fréchet derivative. Under the minimal assumption that the
sought-after ground state eigenvalue is non-degenerate and the associated
ground state eigenfunction is not orthogonal to the chosen reference, we
prove that the continuous coupled cluster equations are {always} locally
well-posed. Under the same minimal assumption and provided that the
discretisation is fine enough, we prove that the discrete {full}-coupled
cluster equations are also locally well-posed, and we derive residual-based
error estimates with {guaranteed} positive constants. These results can
thus be seen as a first step towards developing more refined a posteriori
error estimates for the single-reference coupled cluster method.

*L'exposé **sera donné en personne de 14h à 15h dans** la salle du
séminaire du Laboratoire Jacques-Louis Lions*
Campus Jussieu, Sorbonne Université, 4 place Jussieu, Paris 5ème,
barre 15-16, 3ème étage, salle 09 (15-16-3-09).
*L'exposé sera également diffusé simultanément par Zoom.*

*Identifiants de connexion Zoom :*
*Date et heure :* Vendredi 31 mars 2023 14h00-15h00 (heure de Paris)
*Sujet :* Séminaire LJLL 31 03 2023 M. Hassan
*Lien Zoom pour assister à l'exposé :*
https://us02web.zoom.us/j/89686895150?pwd=UlRIaTBhYUdZc3dsUGlOdW5HN1JtZz09
*ID de réunion :* 896 8689 5150
*Code secret :* 455412

A l'ouverture du lien ci dessus, il est possible que vous soyez placé(e)
pour quelques minutes en « salle d'attente Zoom » en attendant d'être
admis(e) dans la « salle de réunion Zoom » d'où vous pourrez suivre
l'exposé.

*________________________________________Seminaire du Laboratoire
Jacques-Louis LionsSeminaire-du-LJLL a ann.jussieu.fr
<Seminaire-du-LJLL a ann.jussieu.fr>https://www.ljll.math.upmc.fr/fr/seminaires/seminaire_du_laboratoire.html
<https://www.ljll.math.upmc.fr/fr/seminaires/seminaire_du_laboratoire.html>*
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