arXiv subjects

A. S. Lobão Jr

Publications and source records attributed to A. S. Lobão Jr.

8 recordsLinked to original sources

arXiv2023

Cuscuta-Galileon Braneworlds

We investigate braneworlds modeled by topological solutions that arise from the so-called Cuscuta-Galileon model. We develop a first order framework and illustrate our procedure with the scalar field having the well-known hyperbolic tangent profile. We find conditions that must be imposed to the parameters of the model in order to have solutions connecting minima of the potential, with the brane constrained to interpolate Minkowski and anti de Sitter geometries. We also find solutions where the brane only interpolates anti de Sitter geometry. In both cases, the gravity sector of the brane is stable against small fluctuations of the metric.

hep-th↗

arXiv2022

Thick brane models in generalized mimetic gravity

In this work, we investigate braneworld models in mimetic gravity, with the source field having generalized dynamics. We present the mathematical description necessary to study the generalized model and consider the first-order formalism to solve the equations of motion. We also investigate the linear stability of the gravitational sector to verify that the model is stable. In particular, we consider two specific situations where we were able to get exact solutions with a kink-like profile and calculate several important properties of the brane.

hep-th↗

arXiv2022

Generalized Jackiw-Teitelboim gravity in presence of Bloch brane-like models

We investigate generalized Jackiw-Teitelboim gravity, coupling the dilaton field with two scalar matter fields. We obtain the equations of motion of the fields and investigate the linear perturbation of the solutions in general. We study two specific situations that allow analytic solutions with topological behavior and check how the dilaton field, the warp factor and Ricci scalar behave. In particular, we have shown how the parameters can be used to modify the structure of the solutions. Moreover, the perturbations are in general described by intricate coupled differential equations, but in some specific cases we could construct the corresponding zero modes analytically.

hep-th↗

arXiv2022

New Results For Cuscuton Multi-Field Brane

We investigate braneworld models in the presence of the several scalar fields with generalized dynamics. A new mechanism to control the internal structure of brane in modified gravity is used to induce changes in the models in the presence of cuscuton dynamics. Examples with two- and three-field are considered, and we have found that the inclusion of the cuscuton can significantly alter the profile of the brane, causing unique changes in the warp factor, energy density, stability potential and the corresponding zero mode.

hep-th↗

arXiv2022

Mechanism to control the internal structure of thick brane

In this work we study braneworlds generated by several scalar fields. The investigation describes the necessary formalism to examine models and evaluate the conditions for the stability of the gravitational sector under linear perturbations. In particular, we develop a mechanism that help us investigate distinct situations controlled by two and by three fields, focusing on how the fields can be used to modify the internal structure of the brane.

hep-th↗

arXiv2022

Models of modified $F(R,T)$ and cuscuton braneworld

This work deals with braneworld models in the presence of scalar fields in a five-dimensional warped geometry with a single extra dimension of infinite extent. We consider generalized models in the presence of the Ricci scalar, the trace of the stress-energy tensor and the cuscuton contribution. The models describe novel braneworld scenarios and the investigations consider distinct possibilities, from which we show how the brane may change to become thinner, although keeping gravitational stability and the gravity zero mode under strict control. Moreover, we did not identify any split behavior in the warp factor in the presence of the cuscuton and the trace of the stress-energy tensor.

hep-th↗

arXiv2022

Effects of Cuscuton dynamics on braneworld configurations in the scalar-tensor representation of $f\left(R,T\right)$ gravity

In this work we study braneworld configurations in the scalar-tensor representation of the $f\left(R,T\right)$ gravity theory in the presence of a Cuscuton term in the source field matter Lagrangian. We start by deriving the scalar-tensor representation of the theory and obtaining its respective equations of motion. We then introduce the standard metric for a flat braneworld model with one extra dimension for the general case of a $f\left(R,T\right)$ theory and study two different models for the source field. Given the complexity of the field equations, these solutions are obtained numerically. In these cases, the Cuscuton term effectively amplifies the effect, by increasing the height of the stability potential barrier and, consequently, the depth of the minimum of the graviton zero-mode on the brane. Finally, we study the particular cases of $F(R)+T$ and $R+G\left(T\right)$, for which only the scalar fields $φ$ or $ψ$ are present, respectively, and we prove that the presence of the scalar field $φ$ is essential in the development of internal structure on the brane.

gr-qc↗

arXiv2012

Twinlike models for kinks and compactons in flat and warped spacetime

This work deals with the presence of twinlike models in scalar field theories. We show how to build distinct scalar field theories having the same extended solution, with the same energy density and the very same linear stability. Here, however, we start from a given but generalized scalar field theory, and we construct the corresponding twin model, which also engenders generalized dynamics. We investigate how the twinlike models arise in flat and in curved spacetime. In the curved spacetime, we consider a braneword model with the warp factor controlling the spacetime geometry with a single extra dimension of infinite extent. In particular, we study linear stability in the flat and curved spacetime, and in the case of curved spacetime, in both the gravity and the scalar field sectors, for the two braneworld models.

hep-th↗