Made available in DSpace on 2015-04-22T21:56:16Z (GMT). No. of bitstreams: 1 Emanuel Costabile Bezerra.pdf: 5980407 bytes, checksum: 3431184f8d5847b9416becfcb32e3a57 (MD5) Previous issue date: 2012-03-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this paper we investigate the phase diagram of the static and dynamic models of spins, with random field Ising with a bimodal probability distribution, Blume-Capel and Blume- Capel with oscillating external field, using the mean field approximation (MFA) and the effective field (EFT). The thermal properties of balance are theoretically obtained via the mathematical formalism of statistical mechanics of Boltzmann and Gibbs. The stationary states of the kinetic models are described by the stochastic dynamics of Glauber. Using MFA show that the lines in balance first order obtained by Maxwell s construction for the free energy, and out of balance are different. To analyze the stability of sitema the Lyapunov exponent is calculated numerically. In this approach we found values distinct Hc(Dc) for the Ising model with random field (Blume-Capel), ie Hc (static) [Dc (static)] 6= Hc (dynamic) [Dc (dynamic)]. On the other hand, using EFT for first order lines also differ, but now we have Hc (static) [Dc (static)] = Hc (dynamic) [Dc (dynamic)]. We compared our results with the dynamic value of Hc obtained via Monte Carlo simulation out of balance and show that there is a satisfactory agreement in quantitative terms. The energy of the system represented by the Blume-Capel model with oscillating external field does not remain fixed over of evolution, swinging every second of time, so can not obtain the static properties of the formalism of equilibrium statistical mechanics. Returned diagrams phase regions where we find ordered (ferromagnetic), disordered (paramagnetic) and regions of coexistence / Neste trabalho investigaremos o diagrama de fase estatico e dinamico dos modelos de spins: Ising com campo aleatorio com uma distribuicao de probabilidade bimodal, Blume-Capel e Blume-Capel com campo externo oscilante, utilizando as aproximacoes de campo medio (MFA) e de campo efetivo (EFT). As propriedades termicas de equilıbrio sao obtidas teoricamente via o formalismo matematico da mecanica estatıstica de ltzmann e Gibbs. Os estados estacionarios dos modelos cineticos sao descritos pela dinamica estocastica de Glauber. Usando MFA mostramos que as linhas de primeira ordem obtidas no equilıbrio, atraves da construcao de Maxwell para a energia livre, e fora do equilıbrio sao diferentes . A fim de analizar a estabilidade do sitema, o expoente de Lyapunov e calculado numericamente. Nesta aproximacao foram encontrados valores distintos de Hc(Dc) para o modelo de Ising com campo aleatorio (Blume-Capel), isto e, Hc(estatico)[Dc(estatico)]6= Hc(dinamico)[Dc(dinamico)]. Por outro lado, usando EFT as linhas de primeira ordem, tambem diferem, mas agora temos Hc(est´atico)[Dc(est´atico)]= Hc(dinamico)[Dc(dinamico)]. Comparamos nossos resultados da dinamica com o valor de Hc obtido via simulacao de Monte Carlo fora do equilıbrio e mostramos que ha um acordo satisfatorio do ponto de vista quantitativo. A energia do sistema representado pelo modelo Blume-Capel com campo externo oscilante nao permanece fixa ao longo da evolu¸cao, oscilando para todo instante de tempo, portanto, nao e possıvel obter as propriedades estaticas pelo formalismo da mecanica estatıstica do equilıbrio. Obtivemos diagramas de fase onde encontramos regoes ordenadas (ferromagneticas), desordenadas (paramagnetica) e regoes de coexistencia

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