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Ergoregion instability in a fluid with vorticity
Leandro A. Oliveira, Carolina L. Benone, Luís C. B. Crispino
We investigate perturbations in a rotational and incompressible fluid flow. Interested in the phenomenon analogous to the black hole ergoregion instability, we verify the influence…
Static boson stars in the Einstein-Friedberg-Lee-Sirlin theory and their astrophysical images
Pedro L. Brito de Sá, Haroldo C. D. Lima, Carlos A. R. Herdeiro +1
We investigate the static boson star solutions in the so-called Einstein-Friedberg-Lee-Sirlin (E-FLS) theory, performing a complete analysis of the solution space in this model. We…
Singular space-times with bounded algebraic curvature scalars
Renan B. Magalhães, Gabriel P. Ribeiro, Haroldo C. D. Lima Junior +2
We show that the absence of unbounded algebraic curvature invariants constructed from polynomials of the Riemann tensor cannot guarantee the absence of strong singularities. As a c…
Absorption and (unbounded) superradiance in a static regular black hole spacetime
Marco A. A. de Paula, Luiz C. S. Leite, Sam R. Dolan +1
Regular black holes (RBHs) -- geometries free from curvature singularities -- arise naturally in theories of non linear electrodynamics. Here we study the absorption, and superradi…
Superradiant instability of a charged regular black hole
Sam R. Dolan, Marco A. A. de Paula, Luiz C. S. Leite +1
We show that a charged, massive scalar field in the vicinity of an electrically-charged Ayón-Beato-García (ABG) regular black hole has a spectrum of quasibound states that (in a ce…
Twisting shadows: Light rings, lensing and shadows of black holes in swirling universes
Zeus S. Moreira, Carlos A. R. Herdeiro, Luís C. B. Crispino
Using the Ernst formalism, a novel solution of vacuum general relativity (GR) was recently obtained [1], describing a Schwarzschild black hole (BH) immersed in a nonasymptotically…
Geodesic analysis, absorption and scattering in the static Hayward spacetime
Marco A. A. de Paula, Luiz C. S. Leite, Luís C. B. Crispino
We investigate the propagation of massless particles and scalar fields in the background of Hayward regular black holes. We compute the absorption and scattering cross sections and…
Scattering by stringy black holes
Sérgio V. M. C. B. Xavier, Carolina L. Benone, Luiz C. S. Leite +1
We study the scattering of axially incident massless scalar waves by a charged and rotating black hole solution from heterotic string theory called the Kerr-Sen black hole. We comp…
Gravitational bremsstrahlung and the Fulling-Davies-Unruh thermal bath
João P. B. Brito, Luís C. B. Crispino, Atsushi Higuchi
The electromagnetic radiation emitted by an accelerated charged particle can be described theoretically as the interaction of the charge with the so-called Fulling-Davies-Unruh the…
Echoes from bounded universes
Renan B. Magalhães, Andreu Masó-Ferrando, Flavio Bombacigno +2
We construct a general class of modified Ellis wormholes, where one asymptotic Minkowski region is replaced by a bounded 2-sphere core, characterized by asymptotic finite areal rad…
Electrically charged regular black holes in nonlinear electrodynamics: light rings, shadows and gravitational lensing
Marco A. A. de Paula, Haroldo C. D. Lima Junior, Pedro V. P. Cunha +1
Within nonlinear electrodynamics (NED), photons follow null geodesics of an effective geometry, which is different from the geometry of the spacetime itself. Over the last years, s…
Parametrized black holes: Scattering investigation
Renan B. Magalhães, Luiz C. S. Leite, Luís C. B. Crispino
We study the scattering of light-like geodesics and massless scalar waves by a static Konoplya-Zhidenko black hole, considering the case that the parametrized black hole solution c…
Shadows of black holes with dark matter halo
Sérgio V. M. C. B. Xavier, Haroldo C. D. Lima Junior, Luís C. B. Crispino
We investigate the shadow of an exact black hole solution of Einstein's equations recently proposed by Cardoso et al., to describe a supermassive black hole immersed in a dark matt…
Asymmetric wormholes in Palatini gravity: Energy conditions, absorption and quasibound states
Renan B. Magalhães, Andreu Masó-Ferrando, Gonzalo J. Olmo +1
We investigate the absorption properties of reflection-asymmetric wormholes constructed via the thin-shell formalism in Palatini gravity. Such wormholes come from the…
Quasinormal modes of a holonomy corrected Schwarzschild black hole
Zeus S. Moreira, Haroldo C. D. Lima Junior, Luís C. B. Crispino +1
We analyze the quasinormal modes (QNMs) of a recently obtained solution of a Schwarzschild black hole (BH) with corrections motivated by Loop Quantum Gravity (LQG). This spacetime…
Scalar scattering by black holes and wormholes
Haroldo C. D. Lima Junior, Carolina L. Benone, Luís C. B. Crispino
We study the scattering of monochromatic planar scalar waves in a geometry that interpolates between the Schwarzschild solution, regular black holes and traversable wormhole spacet…
Scattering properties of charged black holes in nonlinear and Maxwell's electrodynamics
Marco A. A. de Paula, Luiz C. S. Leite, Luís C. B. Crispino
We investigate the scattering properties of a massless scalar field in the background of a charged Ayón-Beato-García regular black hole solution. Using a numerical approach, we com…
Tidal forces in dirty black hole spacetimes
Haroldo C. D. Lima Junior, Mateus M. Corrêa, Caio F. B. Macedo +1
Black holes can be inserted in very rich astrophysical environments, such as accretion disks. Although isolated black holes are simple objects in general relativity, their accretio…
Compact objects in quadratic Palatini gravity generated by a free scalar field
Renan B. Magalhães, Luís C. B. Crispino, Gonzalo J. Olmo
We study the correspondence that connects the space of solutions of General Relativity (GR) with that of Ricci-based Gravity theories (RBGs) of the type in the metric-affi…
Radiation emitted by a source orbiting a Schwarzschild--anti--de Sitter black hole
J. P. B. Brito, R. P. Bernar, L. C. B. Crispino
We study the scalar radiation emitted by a source orbiting a Schwarzschild--anti--de Sitter black hole in circular geodesics. We obtain the emitted power using quantum field theory…
Absorption by stringy black holes
Sérgio Vinicius M. C. B. Xavier, Carolina L. Benone, Luís C. B. Crispino
We investigate the absorption of planar massless scalar waves by a charged rotating stringy black hole, namely a Kerr--Sen black hole. We compute numerically the absorption cross s…
Einstein-Maxwell-dilaton neutral black holes in strong magnetic fields: topological charge, shadows and lensing
Haroldo C. D. Lima Junior, Jian-Zhi Yang, Luís C. B. Crispino +2
The light rings (LRs) topological charge (TC) of a spacetime measures the number of stable LRs minus the number of unstable LRs. It is invariant under smooth spacetime deformations…
Scattering by deformed black holes
Renan B. Magalhães, Luiz C. S. Leite, Luís C. B. Crispino
Obtaining black hole solutions in alternative theories of gravity can be a difficult task due to cumbersome field equations that arise in many of such theories. In order to study t…
Shadows and lensing of black holes immersed in strong magnetic fields
Haroldo C. D. Lima Junior, Pedro V. P. Cunha, Carlos A. R. Herdeiro +1
We investigate the null geodesic flow and in particular the light rings (LRs), fundamental photon orbits (FPOs) and shadows of a black hole (BH) immersed in a strong, uniform magne…