Expansão em polímeros e suas aplicações a modelos de spins limitados

Abstract

In this dissertation we study the \textit{polymer expansion technique}, which plays a fundamental role in rigorous statistical mechanics, in the study of phase transitions in physical systems. We discuss the pressure analyticity for the \textit{abstract polymer gas model} and, based on the ideas discussed in this model, we make some applications of the technique in other models such as the \textit{subset gas on the lattice $\mathbb{Z}^d$ } and the \textit{Ising model}. We also applied polymer expansion to the Blume-Emery-Griffiths model, in the region of parameters known as \textit{desordered} and we obtained results about analyticity of \textit{free energy} of this model for all temperature.