Statut  Confirmé 
Série  IPNTHEO 
Domaines  nuclth 
Date  Mercredi 10 Avril 2019 
Heure  11:30 
Institut  IPN 
Salle  Bâtiment 100, Salle A015 
Nom de l'orateur  Duguet 
Prenom de l'orateur  Thomas 
Addresse email de l'orateur  
Institution de l'orateur  CEA Saclay 
Titre  Particlenumberprojected Bogoliubov coupled cluster theory: formalism and first application to the Richardson pairing Hamiltonian. 
Résumé  While coupled cluster theory accurately models weakly correlated quantum systems, it often fails in the presence of strong correlations where the standard meanfield picture is qualitatively incorrect. In many cases, these failures can be largely ameliorated by permitting the meanfield reference to break physical symmetries. Symmetrybroken coupled cluster, e.g. Bogoliubov coupled cluster, theory can indeed provide reasonably accurate energetic predictions, but the broken symmetry can compromise the quality of the resulting wave function and predictions of observables other than the energy. Merging symmetry projection and coupled cluster theory is therefore an appealing way to describe strongly correlated systems. One indeed expects to inherit and further improve the energetic accuracy of brokensymmetry coupled cluster while retaining proper symmetries. We present the novel particlenumberprojected Bogoliubov coupled cluster (PBCC) formalism that consistently allows to do so. While the present focus is on U(1) symmetry associated with particle number conservation, a similar formalism is already available to deal with SU(2) symmetry associated with angular momentum. Next, results obtained by testing PBCC on the solvable Richardson pairing Hamiltonian are shown. The very high quality of those results indicates that symmetryprojected coupled cluster is a promising method that can accurately describe both weakly (e.g. doubly closedshell nuclei) and strongly (e.g. singly and doubly openshell nuclei) correlated finite manyfermion systems. 
Numéro de preprint arXiv  
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