Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Série TQM
Domaines math-ph
Date Jeudi 19 Mai 2022
Heure 14:00
Institut LPTHE
Salle LPTHE library Jussieu towers 13-14, 4th floor
Nom de l'orateur Messio
Prenom de l'orateur Laura
Addresse email de l'orateur messio [at] lptmc [dot] jussieu [dot] fr
Institution de l'orateur LPTMC
Titre Overview of the possibilities of high temperature series expansions
Résumé In the search for exotic properties of spin lattices, many numerical methods focus on the ground state and on the low-energy excitations of a model. Here, we use the opposite approach, with high temperature series expansions. The coefficients of the free energy, the specific heat or the magnetic susceptibility series are obtained up to beta^20 (depending on the model complexity). But the convergence radius limits the range of temperature where information can been obtained by simple summation. Thus, alternative methods are required. One of them is the entropy method, that uses some hypothesis on the nature of the ground state to reconstruct thermodynamic quantities over the whole temperature range. This method has been used on several compounds to propose exchange parameter values. When a finite temperature phase transition occurs, a singularity forbids to use the entropy method, but then, informations on the critical exponents and on the critical temperature can be extracted. A review of these methods and their limitations, together with some applications, will be presented.
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