Impact of compactlike and asymmetric configurations of thick branes on the scalar-tensor representation of $f\left(R,T\right)$ gravity

TL;DR

This paper investigates how different configurations of thick branes in $f(R,T)$ gravity influence the scalar-tensor representation, revealing effects on auxiliary fields' behavior and stability, especially in compact and asymmetric models.

Contribution

It introduces a first-order formalism for scalar-tensor $f(R,T)$ brane models and analyzes the impact of compact and asymmetric configurations on auxiliary fields.

Findings

Auxiliary fields show hybrid behavior inside compact branes.

Strong source fields significantly modify auxiliary field solutions.

Asymmetry parameters influence auxiliary field responses.

Abstract

In this work we study braneworld models in generalized $f\left(R,T\right)$ gravity theories where the action depends on a function of the Ricci scalar $R$ and the trace of the stress-energy tensor $T$. We explore the so-called scalar-tensor representation of the theory, where the dependence on $R$ and $T$ are exchanged for two auxiliary real scalar fields. We introduce a first-order formalism to relate the auxiliary fields with the source field of brane and analyze four distinct possibilities of current interest regarding compactification and asymmetry of the brane. We investigate the behavior of the auxiliary fields and their stability in each one of the four cases. For the models where the solution of the source field engenders compact behavior, the auxiliary fields exhibit a hybrid structure, behaving differently inside and outside the compact region described by the source configuration. In particular, we found that the solutions of the auxiliary fields are significantly modified in models where the geometry is strongly influenced by the source field. Moreover, for the model capable of engendering asymmetric features, the two auxiliary fields also respond to modifications on the parameter that controls the asymmetry of the system.