Termodinâmica e estrutura de fases de uma teoria de multicampos escalares na presença de temperatura e potencial químico

Abstract

The possibility that symmetries may be broken (or remain broken) at high temperatures is not new. This phenomenon is usually called inverse symmetry breaking (ISB) or symmetry nonrestoration (SNR) and, it was proposed initially for Weinberg, in 1974, studing a model with two interacting scalarfields infinite temperature. He shows that ISB or SNR is a direct consequence that in two or multifield theories some of the coupling constants betweenfields can be negative while the model is still bounded from below. In 1981, Benson, Bernstein e Dodelson show that ISB or SNR would be found in a model with a complex scalarfield. This happens because in complex scalarsfields model, there are the presence of a conseved charge. In this case, effects of density must be considered and, this effects inducing the emergence of ISB or SNR. Our porpose consist in investigate the phenomenon of inverse symetry brake or symetry non restauration to a model with two interacting complex scalar fields. In a first step, we calculate the one loop aproximation for the effective potential. In the second step, we use the non perturbative approach called OPT, optimized perturbation theory, to calculate the thermal mass up to second order in the expansion. The justification to use a non perturbative approach is that the pertubative expansion can breake down in high temperature. The results obtained for the perturbative case and the non perturbative case are compared and we will show that the results strongly supporting inverse symmetry breaking (or symmetry nonrestoration).