Statut  Confirmé 
Série  TQM 
Domaines  mathph 
Date  Jeudi 19 Mai 2022 
Heure  14:00 
Institut  LPTHE 
Salle  LPTHE library Jussieu towers 1314, 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 lowenergy 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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