Configurações de equilíbrio de cascas finas em teorias escalares-tensoriais

Abstract

As well tested as the theory of General Relativity (GR) maybe, there are still some observations that it cannot satisfactorily explain, such as the accelerated expansion of the universe. Because of this, physicists have been led to consider alternative theories in order to address these complications. Among various theories, in this work, we will be using scalar-tensor theories (TETs). Our goal is to study the equilibrium configurations and types of equilibrium (stable or unstable) of a shell with Minkowski interior and a vacuum solution of TET’s as the exterior, using the formalism of thin shells.This study aims to enable further investigations into quasi-black holes in scalar-tensor theories, considering that thin shells provide an initial modeling for these objects. Additionally, they also model gravitational collapses. We studied the equations of state in the form p = σ and p = γσ2. We found their equilibrium configurations, which allowed us to study the stability of the system and also its compactibility. In the first case, we obtained that all these configurations are stable, and further more, the system always has a compactibility (C) smaller than the limit imposed by TRG (C=1). In the second case, we only obtained stable equilibrium configurations, however, depending on the value of the factor β (which appears in the coupling function), there maybe configurations that are more compact than the TRG limit.