Article
Astronomy & Astrophysics
Edgardo Franzin, Stefano Liberati, Jacopo Mazza, Alex Simpson, Matt Visser
Summary: The recent development of rotating black-bounce-Kerr spacetimes has sparked interest in exploring black-bounce variants of the entire Kerr-Newman family. Specifically focusing on black-bounce-Reissner-Nordstrom and black-bounce-Kerr-Newman spacetimes, researchers have considered their deviation from the Kerr-Newman family in a controlled manner, discussing the existence of Killing tensor and the theoretical impact of non-zero electric charge on astrophysical black holes. Additionally, they have examined the interesting matter/energy content required by the black-bounce-Kerr-Newman solution within the framework of general relativity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Gabriele Bozzola, Vasileios Paschalidis
Summary: Unlike energy and angular momentum, electric charge is conserved in mergers of charged black holes. This paper investigates the formation of naked singularities in quasicircular mergers of charged binary black holes. The theoretical model is extended to estimate the properties of the remnant left by these mergers, and numerical-relativity simulations validate the model's accuracy. The theoretical model suggests that while naked singularities cannot form following these mergers, remnants that are arbitrarily close to the extremal limit can be produced.
Article
Astronomy & Astrophysics
Hamid R. Bakhtiarizadeh
Summary: This study presents the construction of charged rotating black string solutions in four-dimensional Einsteinian cubic gravity for the first time, providing insights into their thermodynamic properties. The solutions are found to be completely regular at the horizon and satisfy the first law of thermodynamics. It is also observed that some solutions have positive specific heat, indicating thermodynamic stability.
Article
Astronomy & Astrophysics
G. Abbas, M. Asgher
Summary: This paper analyzes the tidal effects of anti-de Sitter charged black holes, obtaining the changes in radial and angular tidal forces and presenting the graphical behavior for the most suitable initial conditions.
MODERN PHYSICS LETTERS A
(2022)
Article
Astronomy & Astrophysics
Valerio De Luca, Justin Khoury, Sam S. C. Wong
Summary: This paper investigates the tidal deformability of neutral black holes when nonlinearities in the theory are taken into account. It is found that the tidal Love numbers may be nonvanishing depending on the scalar interactions in the bulk theory.
Article
Physics, Particles & Fields
Xin-Yang Wang, Jie Jiang
Summary: The singularity at the center of charged BTZ black holes, known as a conical singularity, does not disrupt causality of spacetime and should still be surrounded by an event horizon within the black hole.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Pritam Banerjee, Suvankar Paul, Rajibul Shaikh, Tapobrata Sarkar
Summary: Black holes and wormholes, although showing similar Newtonian behaviors at large distances, have different tidal effects on stars when close to the event horizon or throat due to their respective geometries. Quantitative analysis in Schwarzschild black hole and exponential wormhole backgrounds reveals that tidal disruption rates and peak fallback rates of tidal debris are several times higher for wormholes compared to black holes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Lang Liu, Sang Pyo Kim
Summary: We investigate the two-body dynamical capture of black holes with U(1) charge and analyze the gravitational and electromagnetic radiations during this process. By applying a specific formalism, we derive the effects of the charge-to-mass ratio on the merger rate and discover that these effects depend on the models.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Balendra Pratap Singh
Summary: We analytically study the shadow of the charged rotating black hole in the presence of quintessence. The quintessential energy has a significant impact on the shape and size of the black hole shadow, resulting in a distorted dark disk. The factors affecting the black hole shadow include mass, spin, charge, quintessential field parameter, and normalization factor. Our study shows that the black hole shadow monotonically decreases and becomes more distorted with increasing charge, while keeping the spin and normalization factor constant.
Article
Astronomy & Astrophysics
Francesco Paolo Rizzuto, Thorsten Naab, Antti Rantala, Peter H. Johansson, Jeremiah P. Ostriker, Nicholas C. Stone, Shihong Liao, Dimitrios Irodotou
Summary: We performed N-body simulations with post-Newtonian dynamics to study the formation and growth of black holes in low-mass star clusters. The simulations showed that a significant fraction of stars form Bahcall-Wolf cusps, preventing core collapse. Within the first 40 Myr, the systems experienced hundreds to thousands of tidal disruption events (TDEs), with most originating from stars in the Bahcall-Wolf cusp. We derived an analytical formula for the TDE rate and found that TDEs can drive the formation and growth of massive black holes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Mathematics, Interdisciplinary Applications
Edson E. de Souza Filho, Amanda C. Mathias, Ricardo L. Viana
Summary: The deflection of light by a pair of black holes can be seen as an open conservative non-linear dynamic system with chaotic orbits. Analyzing impact parameter and escape angle maps reveals chaotic orbits within specific parameter ranges. Fractal structures are linked to the non-attractive invariant chaotic set present in the system.
CHAOS SOLITONS & FRACTALS
(2021)
Article
Physics, Particles & Fields
Alex Davey, Oscar J. C. Dias, Paul Rodgers
Summary: The article investigates the phase diagram of solutions of the charged black hole bomb system, particularly focusing on static hairy black holes in the Einstein-Maxwell-Scalar theory. These hairy black holes have higher entropy and may serve as the endpoint of instabilities in the black hole bomb system, relating to boson stars in the theory.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Astronomy & Astrophysics
Cai-Ying Shao, Li-Jie Xin, Wei Zhang, Cheng-Gang Shao
Summary: This study examines the validity of strong cosmic censorship (SCC) for the massless scalar field on a charged black hole in an acceleratingly expanding universe driven by quintessence fluid with a constant equation of state parameter. The results show that the violation of SCC occurs as the black hole approaches its extremal limit. Furthermore, the critical value of the black hole charge ratio for such a violation increases with the increase of the energy density amplitude of the quintessence fluid but decreases with the increase of the equation of state parameter. The findings indicate that the violation of SCC occurs not only in asymptotically de Sitter spacetimes but also ubiquitously in a universe with accelerating expansion.
Article
Physics, Multidisciplinary
G. Abbas, M. Asgher
Summary: Tidal forces are the most significant feature of geodesic deviation in General Relativity, especially in relation to tidal disruption events. In this study, we investigate the tidal forces in a black hole described by nonlinear electrodynamic theory. We observe that as the charge of the black hole increases, both the radial and angular components of the geodesic deviation vector also increase. By utilizing the Riemann tensor and geodesic deviation equation, we obtain the components of the tidal force. Furthermore, we solve the geodesic deviation equation for the radial and angular components in an exact black hole spacetime and explore their graphical behavior under different initial conditions and black hole parameters.
Article
Physics, Particles & Fields
Mohammad Reza Alipour, Jafar Sadeghi, Mehdi Shokri
Summary: This paper tackles an important issue concerning the violation of cosmic censorship due to the existence of weak gravity conjecture (WGC). By considering charged black holes in four dimensions and in the normal state, the authors eliminate the violation of weak cosmic censorship conjecture (WCCC) and demonstrate a good compatibility between WGC and WCCC. Furthermore, it is shown that the case with quintessence and cloud of strings has more parameters and more freedom to establish the compatibility between the two theories, compared to the case with only quintessence.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Roberto Casadio, Alexander Kamenshchik, Ibere Kuntz
Summary: The study explores the lack of covariance in the assumptions of the Hawking-Penrose singularity theorem under field redefinitions, proposing to investigate singularities in field space where spacetime singularities might stem from singularities in field-space coordinates. It demonstrates through a specific choice of the DeWitt field-space metric that there may actually be no singularities in pure gravity, attributing vacuum singularities of General Relativity to an unfavorable choice of field variables.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Physics, Particles & Fields
Roberto Casadio, Ibere Kuntz, Gregorio Paci
Summary: This article studies the quantization of matter fields in a background described by the teleparallel equivalent to general relativity. The presence of local Lorentz and gauge symmetries leads to different coupling prescriptions, which are analyzed separately. As expected, quantum matter fields produce divergences that cannot be absorbed by terms in the background action. However, the formulation of teleparallel gravity allows for the identification of the problem's source. By imposing local Lorentz invariance after quantization, it is shown that a modified teleparallel gravity can be renormalized at one-loop order without introducing higher-order terms, thus preventing the appearance of ghosts in the theory.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Mathematical
Roberto Casadio
Summary: Researchers attempt to reconstruct the state of a Schwarzschild black hole by analyzing a collapsing ball of dust and describing the outer geometry using a coherent state.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Review
Astronomy & Astrophysics
Ibere Kuntz, Roberto Casadio, Alexander Kamenshchik
Summary: The lack of covariance under field redefinitions in the Hawking-Penrose theorem raises questions about the nature of spacetime singularities. This review explores the concept of covariant singularities, which are invariant under both spacetime diffeomorphisms and field redefinitions.
MODERN PHYSICS LETTERS A
(2022)
Article
Physics, Multidisciplinary
Xavier Calmet, Roberto Casadio, Stephen D. H. Hsu, Folkert Kuipers
Summary: Explored the relationship between the quantum state of a compact matter source and its asymptotic graviton field. Established the existence of ubiquitous quantum hair due to gravitational effects.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Andrea Giusti, Silvia Buffa, Lavinia Heisenberg, Roberto Casadio
Summary: The quantum description of a toy model universe with Schwarzschild-de Sitter geometry arising from the coherent state of a massless scalar field is considered. The study reveals clear hints that the reaction of the de Sitter background to matter sources induces modified Newtonian dynamics at galactic scales and different measured values for the present Hubble parameter.
Article
Physics, Multidisciplinary
Roberto Casadio, Octavian Micu, Jonas Mureika
Summary: This study investigates the possible existence of a Newtonian regime of gravity in 1 + 1 dimensions, examining metrics in both the Kerr-Schild and conformal forms. In the Kerr-Schild case, the metric provides an exact solution to the Poisson equation in flat space, but the weak-field limit and non-relativistic regime of geodesic motion are not trivial. By utilizing harmonic coordinates, the metric is shown to be conformally flat and a weak-field expansion becomes straightforward. However, the analysis of the non-relativistic regime of geodesic motion remains complex, and the weak-field potential only approximately satisfies the flat space Poisson equation.
Article
Physics, Multidisciplinary
Roberto Casadio, Alexander Kamenshchik, Ibere Kuntz
Summary: This passage points out that a full-fledged theory of quantum gravity should possess background independence and diffeomorphism invariance. However, any path-integral approach to quantum gravity leads to a tension between these properties, making it impossible to satisfy them simultaneously.
Article
Physics, Multidisciplinary
R. Casadio, L. Tabarroni
Summary: We study the impact of rotation on the spectrum of bound states for dust cores that generate (quantum) black holes recognized in Eur. Phys. J. C 82 (2022) 10. The analysis assumes a slowly rotating dust ball, allowing for the use of perturbation theory. The study reveals that the total angular momentum of the system, like the total mass, is quantized in Planck units, leading to quantized horizon area. For sufficiently small mass in the outer layer, the model permits ground states that rotate fast enough within the perturbative regime to describe regular rotating objects rather than black holes.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
R. Casadio, R. da Rocha, P. Meert, L. Tabarroni, W. Barreto
Summary: Two types of information entropy in the quantum states of a black hole's matter core are studied. The quantum mechanical picture of a collapsing ball of dust in general relativity, including a non-trivial ground state and a spectrum of bound states, is described. Computed information entropies shed new light on the stability of the ground state and the spectrum of higher excited states.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Astronomy & Astrophysics
Roberto Casadio, Wenbin Feng, Ibere Kuntz, Fabio Scardigli
Summary: This article discusses the concepts of minimum geometrical length and minimum length scale in quantum field theory, using correlation functions obtained from in-in and in-out amplitudes. The in-in propagator for metric perturbations does not admit the former, while the in-out Feynman propagator shows the emergence of the latter. The article then exhibits a connection between the Feynman propagator of quantum field theories of gravity and the deformation parameter 80 of the generalized uncertainty principle (GUP), allowing for the determination of an exact expression for 80 in terms of the residues of the causal propagator. A conjecture is made about the correspondence between the non-renormalizability of (some) theories of gravity and the existence of a minimum length scale, suggesting that non-renormalizable theories are self-complete and finite. The role of the sign of the deformation parameter is further discussed by considering the implementation of the GUP on the lattice.
Article
Physics, Particles & Fields
Roberto Casadio, Andrea Giusti, Jorge Ovalle
Summary: We study black holes formed by quantum matter with regular wavefunctions. This leads to integrable energy densities and the absence of Cauchy horizons in spherically symmetric configurations. Additionally, we discover that the ultrarigid rotation of Kerr spacetime results in the presence of an inner horizon in rotating systems, and we analyze the general properties of quantum matter cores at the center of rotating black holes, which exhibit integrable singularities and no Cauchy horizon.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Jorge Ovalle, Roberto Casadio, Andrea Giusti
Summary: This paper examines static and stationary regular black holes that satisfy two requirements: the presence of a well-defined event horizon and matter that satisfies the weak energy condition. Using the gravitational decoupling approach, the authors find non-singular hairy solutions and identify the matter source responsible for deforming the Minkowski vacuum, with the maximum deformation corresponding to the Schwarzschild solution for the static case and the Kerr metric for the stationary case.
Article
Physics, Particles & Fields
R. Casadio, R. da Rocha
Summary: The minimal geometric deformation (MGD) paradigm is used to study axion stars on fluid branes. The finite value of the brane tension corrects the density, compactness, radius, and asymptotic limit of the gravitational mass function of axion stars in a MGD background. The brane tension also enhances the effective range and magnitude of the axion field coupled to gravity. MGD axion stars are compatible with mini-massive compact halo objects within the observational range of brane tension, but only a narrow range allows for MGD axion star densities high enough to produce stimulated decays of the axion to photons, which has no analogy in the general-relativistic (GR) limit. Additionally, the gravitational mass and density of MGD axion stars are shown to be up to four orders of magnitude larger than the GR axion stars and less sensitive to tidal disruption events under collision with neutron stars, for lower values of the fluid brane tension.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Roberto Casadio, Ibere Kuntz, Octavian Micu
Summary: This study examines binary mergers in bootstrapped Newtonian gravity, where higher-order couplings are introduced to the non-relativistic Lagrangian. The theory's interpretation of astrophysical and cosmological events is affected by the difference between the Arnowitt-Deser-Misner mass and the proper masses in both Newtonian gravity and general relativity. The findings also demonstrate that LIGO's observations, including the GW150914 signal, do not violate the mass gap.
