arXiv subjects

A. C. L. Santos

Publications and source records attributed to A. C. L. Santos.

6 recordsLinked to original sources

arXiv2024

Generating 4-dimensional Wormholes with Yang-Mills Casimir Sources

This work presents a new wormhole solution in General Relativity supported by the quantum vacuum fluctuations of the Casimir effect between perfect chromometallic mirrors in $(3+1)$ dimensions, which was recently fitted using first-principle numerical simulations. Initially, we employ a perturbative approach for $x = m r \ll 1$, where $m$ represents the Casimir mass. This approach has proven to be a reasonable approximation when compared with the exact case in this regime. To find well-behaved redshift functions, we impose constraints on the free parameters. As expected, this solution recovers the electromagnetic-like Casimir solution for $m = 0$. Analyzing the traversability conditions, we graphically find that all will be satisfied for $ 0 \leq m \leq 0.20$. On the other hand, all the energy conditions are violated, as usual in this context. Stability from Tolman-Oppenheimer-Volkov (TOV) equation is guaranteed for all $r$ and from the speed of sound for $0.16 \le m \le 0.18$. Therefore, for $0.16 \leq m \leq 0.18$, we will have a stable solution that satisfies all traversability conditions.

gr-qc↗

arXiv2023

Regular Black Holes in $D=2+1$ with $f(R)$ Gravity

Despite the experimental success of general relativity in the scales it has been tested, there are still some inconsistencies, such as explaining the acceleration of the universe and singularities. $f(R)$ gravity has emerged to provide corrections to the Ricci scalar, leading to new equations of motion that could explain this acceleration. On the other hand, Regular Black Holes, supported by non-linear electrodynamics, have well-defined curvature scalars but often violate energy conditions. In this work, we investigate how to obtain regular solutions in $(2+1)$ dimensions by considering $f(R)$ gravity and non-linear electrodynamics. Subsequently, we find that non-linear electrodynamics models that guarantee regular solutions in General Relativity do not produce regular solutions in $f(R)$ theory. Finally, we observe that energy conditions are still violated in $f(R)$ gravity.

gr-qc↗

arXiv2022

A new class of regular black hole solutions with quasi-localized sources of matter in $(2 + 1)$ dimensions

This paper investigates a new class of regular black hole solutions in (2 + 1)-dimensions by introducing a generalization of the quasi-localized matter model proposed by Estrada and Tello-Ortiz. Initially, we try to physically interpret the matter source encoded in the energy-momentum tensor as originating from nonlinear electrodynamics. We show, however, that the required conditions for the quasi-locality of the energy density are incompatible with the expected behavior of nonlinear electrodynamics, which must tend to Maxwell's theory on the asymptotic limit. Despite this, we propose a generalization for the quasi-localized energy density that encompasses the existing models in the literature and allows us to obtain a class of regular black hole solutions exhibiting remarkable features on the event horizons and their thermodynamic properties. Furthermore, since the usual version of the first law of thermodynamics, due to the presence of the matter fields, leads to incorrect values of entropy and thermodynamics volume for regular black holes, we propose a new version of the first law for regular black holes.

gr-qc↗

arXiv2022

Remarks on the effects of the quintessence on regular black holes

We present the generalization of a regular black hole surrounded by quintessence, considering Bardeen-like solutions added with this fluid. We also compare our solution particularized to the Bardeen one with those found in the recent literature, showing that some of them are inconsistent since they add quintessence "by hand", neglecting also the interesting behavior of the complete solution nearby the origin. Then, we present the correct way to implement the quintessential fluid in more general four-dimensional regular black hole geometries and explore some of its consequences, such as removing the black hole regularity at the origin.

gr-qc↗

arXiv2021

Casimir Effect Nearby and Through a Cosmological Wormhole

In this letter, we investigate the changes in the quantum vacuum energy density of a massless scalar field inside a Casimir cavity that orbits a wormhole, by considering the cosmological model with an isotropic form of the Morris-Thorne wormhole, embedded in the FLRW universe. In this sense, we examine the effects of its global curvature and scale factor in an instant of the cosmic history, besides the influences of the local geometry as well as of inertial forces, on the Casimirenergy density. We also study the behavior of this quantity when each plate is fixed without rotation at the opposite sides of the wormhole throat, at zero and finite temperatures, taking into account the effective distance between the plates through the wormhole throat.

gr-qc↗

arXiv2021

Casimir Effect in a Schwarzschild-Like Wormhole Spacetime

In this paper, we investigate the role of gravito-inertial effects on the Casimir energy of a massless scalar field confined between two parallel plates orbiting a static and zero tidal Schwarzschild-like wormhole, at zero temperature. Firstly, we obtain the metric in isotropic coordinates, finding the allowed angular velocities and the circular orbit radii for a material particle as well as for the photon. Following, we compute the changes induced by both gravity and rotation of the plates in the energy density of the quantum vacuum fluctuations associated to the scalar field, in the zero tidal approximation inside the cavity. Finally, the Casimir energy obtained for some these wormholes are graphically compared between themselves and also with those ones related to an Ellis wormhole as well as to a Schwarzschild black hole. With this, the gravito-inertial effects on the quantum vacuum fluctuations analyzed in this work allow to recognize and identify both the geometry and topology of the spacetime associated to each one of these objects.

gr-qc↗