Made available in DSpace on 2014-12-17T15:14:53Z (GMT). No. of bitstreams: 1 EzequielSS_TESE_1-36.pdf: 2833138 bytes, checksum: 8dff967d0db53770cafa5d4706ea80e4 (MD5) Previous issue date: 1988-08-19 / A real space renormalization group method is used to investigate the criticality (phase diagrams, critical expoentes and universality classes) of Z(4) model in two and three dimensions. The values of the interaction parameters are chosen in such a way as to cover the complete phase diagrams of the model, which presents the following phases: (i) Paramagnetic (P); (ii) Ferromagnetic (F); (iii) Antiferromagnetic (AF); (iv) Intermediate Ferromagnetic (IF) and Intermediate Antiferromagnetic (IAF). In the hierarquical lattices, generated by renormalization the phase diagrams are exact. It is also possible to obtain approximated results for square and simple cubic lattices. In the bidimensional case a self-dual lattice is used and the resulting phase diagram reproduces all the exact results known for the square lattice. The Migdal-Kadanoff transformation is applied to the three dimensional case and the additional phases previously suggested by Ditzian et al, are not found / A t?cnica do grupo de renormaliza??o no espa?o real ? usada para estudar as propriedades criticas (diagramas de fases, expoentes cr?ticos e universalidade) do modelo ZC4D em duas e tr?s dimens?es. Os valores dos par?metros de intera??o s?o escolhidos de modo a obter os diagramas de fases completos do modelo, o qual apresenta as fases: (i) Paramagn?tica (P); (ii) Ferromagn?tica (F); (iii) Antiferromagn?tica (AF); (iv) Intermedi?ria Ferromagn?tica (IF) e (V) Intermedi?ria Antiferromagn?tica (IAF). Os resultados obtidos s?o exatos nas redes hier?rquicas, geradas pela renormaliza??o, e servem como aproxima??es para as redes quadrada e c?bica simples. No caso bidimensional um grafo autodual ? usado e o diagrama de fases obtido reproduz todos os resultados exatos conhecidos para a rede quadrada. Uma transforma??o de Midgal- Kadanoff ? aplicada ao estudo do caso tridimensional e as fases adicionais sugeridas por Ditzian et. al n?o s?o encontradas