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Previous issue date: 2008-11-14 / High-precision calculations of the correlation functions and order parameters were performed in order to investigate the critical properties of several two-dimensional ferro-
magnetic systems: (i) the q-state Potts model; (ii) the Ashkin-Teller isotropic model; (iii) the spin-1 Ising model.
We deduced exact relations connecting specific damages (the difference between two microscopic configurations of a model) and the above mentioned thermodynamic quanti-
ties which permit its numerical calculation, by computer simulation and using any ergodic dynamics. The results obtained (critical temperature and exponents) reproduced all the known values, with an agreement up to several significant figures; of particular relevance were the estimates along the Baxter critical line (Ashkin-Teller model) where the exponents have a continuous variation. We also showed that this approach is less sensitive to the
finite-size effects than the standard Monte-Carlo method.
This analysis shows that the present approach produces equal or more accurate results, as compared to the usual Monte Carlo simulation, and can be useful to investigate these models in circumstances for which their behavior is not yet fully understood / Atrav?s de c?lculos de alta precis?o das fun??es de correla??o e dos par?metros de ordem, investigamos as propriedades cr?ticas de v?rios modelos ferromagn?ticos bidimensionais, a saber: (i) Potts q-estados; (ii) Ashkin-Teller isotr?pico; (iii) Ising de spin-1. Utilizamos simula??es computacionais, obtidas a partir de rela??es anal?ticas exatas, conectando as quantidades acima mencionadas e certas combina??es de Danos (diferen?as
entre duas configura??es microsc?picas de um modelo), que s?o v?lidas para qualquer din?mica erg?dica.
Todos os resultados encontrados (temperaturas e expoentes cr?ticos) concordam com os valores conhecidos, em v?rias casas decimais, destacando-se em particular a reprodu??o da linha de Baxter (no caso ii) onde os expoentes variam continuamente, resultado de
dif?cil obten??o por m?todos tradicionais. Tamb?m mostramos que este m?todo ? menos sens?vel aos efeitos de tamanho finito que aqueles baseados no procedimento usual de simula??o de Monte-Carlo. Tais fatos indicam a potencialidade desta abordagem para
investigar situa??es ainda insuficientemente exploradas, nos modelos acima analisados e em outros semelhantes
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/16535 |
| Date | 14 November 2008 |
| Creators | Anjos Filho, Ant?nio Soares dos |
| Contributors | CPF:07136200482, http://lattes.cnpq.br/7218040405934056, Nobre, Fernando Dantas, CPF:13068164400, http://lattes.cnpq.br/2007917360087831, Souza, Adriano de Oliveira, CPF:38816687304, http://lattes.cnpq.br/5538200920343666, Costa, Francisco Alexandre da, CPF:27023320482, http://lattes.cnpq.br/5307397723573993, Oliveira, Ant?nio Jos? Silva, CPF:07496125334, http://lattes.cnpq.br/8425084108120335, Mariz, Ananias Monteiro |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em F?sica, UFRN, BR, F?sica da Mat?ria Condensada; Astrof?sica e Cosmologia; F?sica da Ionosfera |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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