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Une approche non perturbative de systèmes frustrés et de systèmes désordonnés

Abstract : The main part of this work consists in the study of spins submitted to competing interactions, and which are therefore frustrated. We give a detailed description of the experimental and numerical situation. We emphasize on the fact that it is necessary to go beyond perturbation theory for understanding the physical behavior of these systems. \\\indent A non-perturbative approach is therefore needed. We describe such an approach, based on an exact renormalization group equation. We discuss in details the case of vectorial models in order to show how this approach is implemented in practice, and to stress on its outstanding features. While studying frustrated systems, this non-perturbative approach indicates that these systems exhibit a weakly first order phase transition, in good agreement with experimental and numerical results. We present in the last chapter a study of the Ising model in presence of non-magnetic impurities by using the same non-perturbative approach.
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Contributor : Matthieu Tissier <>
Submitted on : Tuesday, January 22, 2002 - 2:46:59 PM
Last modification on : Wednesday, December 9, 2020 - 3:08:32 PM
Long-term archiving on: : Wednesday, November 23, 2016 - 9:43:48 AM


  • HAL Id : tel-00001045, version 1


Matthieu Tissier. Une approche non perturbative de systèmes frustrés et de systèmes désordonnés. Analyse de données, Statistiques et Probabilités []. Université Paris-Diderot - Paris VII, 2001. Français. ⟨tel-00001045⟩



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