113 leaves : diags ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mathematical Physics, 1979

Thesis (Ph.D.)--University of Adelaide, Dept. of Mathematical Physics, 1979.

Mainz, Univ., Diss., 2000. / Computerdatei im Fernzugriff.

Mainz, Univ., Diss., 2000. / Computerdatei im Fernzugriff.

Mainz, Universiẗat, Diss., 2000.

Orientador: Gustavo A. T. F. da Costa / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin" / Made available in DSpace on 2018-07-28T05:47:04Z (GMT). No. of bitstreams: 1 VarianeJunior_Joao_M.pdf: 1079973 bytes, checksum: e77263f9a3078cb0bf836a20a358dbd7 (MD5) Previous issue date: 1997 / Resumo: A Identidade de Feynman relaciona certos tipos de gráficos e caminhos fechados sobre uma rede quadrada. Inicialmente conjecturada por Feynman, esta relação é importante no cálculo da função de partição do Modelo de Ising dentro da chamada formulação combinatorial do modelo. Nesta tese um caso particular e não trivial desta identidade é investigado. Neste caso, a rede tem apenas um vértice e R arestas com todas as extremidades ligadas a ele. A existência da identidade neste caso é provada e alguns problemas até então em aberto sobre ele são resolvidos / Abstract: Feynman identity relates certain types of graphs with closed paths over a squared lattice. Originally conjectured by Feynman, this identity is a important. element in the combinatorial formulation of the Ising Model and in the computation of the partition function of the model within this formulation. In this Thesis a particular but nontrivial case of the identity is investigated. In this case, the lattice has only one site and R edges linked to it. The existence of the identity in this case is proved and some open problems related with it are solved. / Mestrado / Física / Mestre em Física

Dans cette thèse on étudie le comportement métastable de la dynamique de Glauber pour le modèle d'Ising en dimension deux, dans le régime où la température est fixée à une valeur sous critique et le champ magnétique extérieur est très petit. En volume infini, ce modèle a été étudié par Schonmann et Shlosman qui montrent le lien existant entre le temps moyen de transition et la tension de surface intégrée de la forme de Wulff. Cependant, l'exponentialité du temps de transition, déjà en volume fini, reste un problème ouvert. Dans cette thèse on adresse cette question. On donne d'abord un cadre théorique pour traiter ces dynamiques markoviennes métastable pour lesquelles le support de la mesure métastable n'est pas réductible à une seule configuration. Nos techniques permettent d'obtenir la loi exponentielle du temps de transition ainsi que d'estimer sa moyenne et le temps de relaxation de la dynamique. Dans la deuxième partie de notre travail on s'adresse à la dynamique de Glauber métastable; on donne les bonnes définitions des ensemble métastable et stable et on estime les temps de relaxation des dynamiques restreintes à ces deux ensembles. Cela nous permet de mettre en œuvre les techniques étudiées dans la première partie du travail. Nos résultats sont vrais pour toute température sous critique et pour une grande classe de mesure de départ / In this thesis we study the metastable behavior of the Glauber dynamics for the two-dimensional Ising model in the regime where the temperature is kept fixed at some subcritical value and the external magnetic field is vanishing.In the infinite volume regime, this model has been studied by Schonmann and Shlosman who show the connection between the mean transition time and the integrated surface tension of the Wulff shape. However, the exponentiality of the transition time, already in the finite volume case, is still an open problem. In this thesis we address this question.First, we give a theoretical framework to deal with metastable markovian dynamics such that the support of the metastable measure is not reducible to a single configuration. Our techniques allow to get the exponential law of the transition time as well as to estimate its mean and the relaxation time of the dynamics. In the second part of the thesis we address the metastable Glauber dynamics; we give suitable definitions of the metastable and the stable sets and we estimate the relaxation time of the dynamics restricted to these two sets. In doing so, we are in good shape to exploit the techniques studied in the first part of our work. Our results hold true for any subcritical temperature and a wide class of starting measures

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Linda E. Reichl. Vita. Includes bibliographical references. Also available from UMI.

Not available / text

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references (leaves 172-179). Also available in an electronic version.