Symmetric Charged Black Hole Research Articles

Quantum instability of the Cauchy horizon in a charged de-Sitter spacetime with dark matter

The strong cosmic censorship conjecture (SCCC) requires that spacetime cannot be extended beyond the Cauchy horizon. This ensures the predictability of spacetime. In this paper, we investigate the SCCC for a spherically symmetric charged de-Sitter black hole surrounded by dark matter using classical and quantum scalar fields. At the classical level, we analyze the behavior of scalar waves near the Cauchy horizon using the method developed by Hintz and Vasy. We find a relationship between the Sobolev regularity of scalar waves and the spectral gap of quasinormal modes. In the nearly extremal region, this may lead to a violation of the SCCC. At the quantum level, we first provide a proof of the renormalizability of the quantum scalar field in dark-matter black holes. Using numerical methods, we then demonstrate that the renormalized quantum stress-energy tensor for any Hadamard state exhibits quadratic divergence near the Cauchy horizon in the nearly extremal region. The quadratic divergence of the renormalized quantum stress-energy tensor is sufficient to convert the Cauchy horizon into a singularity. Thus, the SCCC is preserved by quantum effects. Since the quadratic divergence is more singular than the behavior of classical scalar field perturbations near the Cauchy horizon, it means there is a region where physics is dominated by quantum effects. We study the influence of dark matter on quantum effects in this region and we find there is a monotonic relationship between the dark matter and the strength of quantum effects. The numerical results show that the quantum effects will become stronger as dark matter increases.

Static black hole in minimal Horndeski gravity with Maxwell and Yang-Mills fields and some aspects of its thermodynamics

In this work we obtain a static spherically symmetric charged black hole solution in the framework of minimal Horndeski gravity with additional Maxwell and Yang-Mills fields. The obtained solution is examined; in particular, its asymptotics are studied. Thermodynamics of the black hole is investigated, namely, we use an effective surface gravity to derive black hole temperature. To obtain the first law of black hole thermodynamics, the Wald method is applied. We also use the extended thermodynamics approach, namely, it allows us to derive the Smarr relation, Gibbs free energy, and the thermal equation of state. The study of thermal values in the extended space shows rich phase behavior, in particular, the domain where the first-order phase transition takes place and the critical point with the second-order phase transition. We also study thermal behavior near the critical point, obtain critical exponents, and analyze the Ehrenfest equations at the critical point. Finally, we calculate the Prigogine-Defay ratio confirming the conclusion about the second-order phase transition at the critical point. Published by the American Physical Society 2024

Exact analytical quasibound states of a scalar particle around a Reissner-Nordström black hole

In this paper, we investigate behavior of massive and massless scalar particle around a static spherically symmetric charged black hole—so called Reissner-Nordström black hole in 3+1 dimension. We successfully discover a novel exact analytical quasibound states' wave functions and energy levels by solving the covariant Klein-Gordon wave equation. The quasibound state has complex-valued energy E=ER+iEI where the real part ER can be interpreted as the scalar particle's energy while the imaginary part represents the decay. We also discuss the Hawking radiation from the apparent horizon of Reissner-Nordström black hole which can be calculated using the scalar particle's wave function. In principle, this study could provide the possibility for laboratory testing of effects whose nature is absolutely related with quantum effects in gravity.

Matter accretion onto charged black holes in symmergent gravity

In astrophysics, accretion is a process where the black hole acquires matter. The gravitational energy is released as a result of the accretion and converted into radiation. Accretion onto dark compact objects, for example, neutron stars, white dwarfs, and black holes is a significant process in the astrophysical phenomenon. It is a fruitful way to examine the features of modified gravity theories by testing the analysis of their results related to dark compact objects. Here, we study the motion of a charged particle moving in near a charged symmergent black hole with Maxwell field. The symmergent gravity is a newly developed modified theory gravity within the framework of the vacuum energy VO, gravitational constant G, and quadratic curvature coefficient cO. The vacuum energy VO can be defined in terms of G and cO in the case where all the fields are degenerate in the form of mass. Further, two different choices of the parameter α provide us two different black hole spacetimes, like de Sitter for α<1 and anti-de Sitter for α>1. For this, we explore the accretion of perfect fluid onto the spherically symmetric charged symmergent black hole. Then, we get analytical results among the four-velocity and energy densities of the accreting matter. Further, we investigate it for well-known fluids flowing onto a charged symmergent black hole. Applying the Hamiltonian approach, we are able to explore the nature of accretion for these fluids such as ultra-stiff fluid, ultra-relativistic fluid, radiation fluid, and sub-relativistic fluid onto the source mass. For this study, we classified isothermal types of fluid in the context of equations of state. In addition, we introduced the application of polytropic test fluid associated with accretion disks. The accretion rate is analyzed near a charged symmergent black hole, which produced a typical behavior presented graphically by the significant parameters α and Q.

Thermodynamics of Charged Black Hole in Symmetric Teleparallel Gravity

AbstractIn the current study, we examine the thermodynamics of a novel symmetric teleparallel gravity charged black hole solution. Our main focus is on the approximated solution for a nonlinear model like . For this purpose, we calculate the Hawking temperature and discuss the stable configuration of considered black hole using heat capacity. Then, we explore the effects of thermal corrections on thermodynamical quantities as well as energies of the system. We study the phase transitions of the system in the background of thermal fluctuations. It is concluded that the presence of coupling constant enhances the thermodynamical stable configuration of uncharged and charged BH geometries. To complete this study, we also explore the interesting aspects of the emission energy and quantum fluctuations. We highlight that our results are in good agreement with the thermodynamics of the previous black hole solutions and assumptions presented in the literature.

СИЛЬНОЕ ГРАВИТАЦИОННОЕ ЛИНЗИРОВАНИЕ ДЛЯ СЛУЧАЯ РЕГУЛЯРНЫХ ЗАРЯЖЕННЫХ ЧЕРНЫХ ДЫР БЕЗ ГОРИЗОНТА

Gravitational lensing often becomes one of the ways to experimentally test a particular theory of gravity, since it allows a visual comparison of theoretical predictions with observational data. The more massive the compact object, the stronger the visible effects are; for this reason, it seems very promising to study strong gravitational lensing by sources such as supermassive black holes. The aim of this paper is to study gravitational lensing for the case of spherically symmetric regular charged black holes with 0 &lt; b ≤ bE and compare the obtained parameters with those calculated for spacetime without a horizon ( b &gt; bE). Here b is an additional parameter describing the charge, and its value b = bE = 0.226 corresponds to the boundary case when the horizon disappears. In addition, using the massive objects Phe A* and M104* as an example, as well as the elliptical galaxies NGC57 and NGC163, we will compare the observed characteristics of regular charged and ordinary Schwarzschild black holes: the angular position of the asymptotic relativistic images, the angular distance between them and those calculated for the same b most images that are farthest from the center, as well as zooming in on the farthest images. The results obtained can later be compared with observational data, which will allow us to conclude that the approach used is applicable within the framework of the theory under consideration.

Nonperturbative quantum correction to the Reissner-Nordström spacetime with running Newton’s constant

We study the consequences of the running Newton's constant on several key aspects of spherically symmetric charged black holes by performing a renormalization group improvement of the classical Reissner-Nordstr\"om metric within the framework of the Einstein-Hilbert truncation in quantum Einstein gravity. In particular, we determine that the event horizon surfaces are stable except for the extremal case and we corroborate the appearance of a new extremality condition at the Planck scale that contributes to hints about the possible existence of a final stage after the black hole evaporation process. We find explicit expressions for the area and surface gravity of the event horizon and we show the existence of an exact form $dS$ with the surface gravity as integrating factor, in contrast to a previous no-go result for axially symmetric spacetimes with null charge. As a consequence, we are able to derive a formula for the state function $S$ as the sum of the area of the classical event horizon plus a quantum correction linear in $\ensuremath{\hbar}$ and logarithmic in the classical area, in accordance with other approaches. We finally calculate an explicit formula for the Komar mass at the event horizon, and we compare it with the total mass at infinity for a wide domain of values of the black hole parameters $M$, $Q$ and $\overline{w}$, showing a loss of mass which can be interpreted as a consequence of the antiscreening effect of the gravitational field between the event horizon and infinity.

Shadow of a charged black hole with scalar hair

Seeking singularity free solutions are important for further understanding black holes in quantum level. Recently, a five-dimensional singularity free black hole/topological star was constructed (Bah and Heidmann in Phys Rev Lett 126:151101, 2021). Through the Kaluza–Klein reduction, an effective four-dimensional static spherically symmetric charged black hole with scalar hair can be obtained. In this paper, we study shadow of this charged black hole with scalar hair in terms of four kinds of observers, i.e., static observers, surrounding observers, freely falling observers, and escaping observers in four-dimensional spacetime. For a spherically symmetric black hole, the shadow is circular for any observer, but the shadow size depends on the motion status of the observer. On the other hand, the effect of plasma is also investigated by a simple model. The radius of the photon sphere depends on the plasma model. Most importantly, we find that the shadow sizes do not monotonically decrease with r in some cases.

Quasinormal modes of charged black holes with corrections from nonlinear electrodynamics

We study quasinormal modes related to gravitational and electromagnetic perturbations of spherically symmetric charged black holes in nonlinear electrodynamics. Beyond the linear Maxwell electrodynamics, we consider a class of Lagrangian with higher-order corrections written by the electromagnetic field strength and its Hodge dual with arbitrary coefficients, and we parametrize the corrections for quasinormal frequencies in terms of the coefficients. It is confirmed that the isospectrality of quasinormal modes under parity is generally violated due to nonlinear electrodynamics. As applications, the corrections for quasinormal frequencies in Euler-Heisenberg and Born-Infeld electrodynamics are calculated, then it is clarified that the nonlinear effects act to lengthen the oscillation period and enhance the damping rate of the quasinormal modes.

Spherically symmetric charged black holes with wavy scalar hair

We study standard Einstein–Maxwell theory minimally coupled to a complex valued and self-interacting scalar field. We demonstrate that new, previously unnoticed spherically symmetric, charged black hole solutions with scalar hair exist in this model for sufficiently large gravitational coupling and sufficiently small electromagnetic coupling. The novel scalar hair has the form of a spatially oscillating ‘wave packet’ and back-reacts on the space-time such that both the Ricci and the Kretschmann scalar, respectively, possess qualitatively similar oscillations.

Geodesic study of spherically symmetric black holes in Palatini-type gravity

This paper probes the geodesic structure of spherically symmetric charged black holes using modified theory of gravity. We explore the geodesic structures of different black holes in the background of Palatini [Formula: see text] theory as well as Eddington-inspired Born–Infeld gravity. We have examined the stability of orbits with the analysis of effective potential. The impacts of modified gravity on particle dynamics specially the circular orbits, the deflection angle and trajectory followed by lightlike as well as for timelike particles are scrutinized. We find that the orbits are more stable for the large values of charge and Born–Infeld parameter.

Dynamical motion of matter around a charged black hole

We investigate the dynamical motion of test particles and accretion processes around spherically symmetric charged black hole. We first show the derivation of the Paczyňski–Wiita (PW) potential for any spherically symmetric spacetime and present analytical form of the PW potential in the Reissner–Nordström (RN) spacetime and the RN-type spacetime. We study the dependence of the characteristic orbits of test (neutral and charged) particles around a charged black hole from two main parameters, namely, charge of RN black hole and the interaction of charged particle with the external electromagnetic field of the black hole and present graphical trajectories of test particles around the black hole. It is shown that with increasing the absolute value of interaction parameter, [Formula: see text], the innermost stable circular orbit (ISCO) radius for charged particle always increases. It is also shown that the energy efficiency for a charged particles can reach up to [Formula: see text] in the presence of an external charged black hole, while for neutral particles it can reach up to [Formula: see text] for neutral particles. The capture cross-section of the photon is by the charged black and the optical appearance of the thin accretion disk around the charged black. Finally, we have studied the flux energy and the thermal spectrum of the accretion disk consisting of the polytropic gas, around the charged black hole.

Gravitational energy of the spherically symmetric static and charged black holes encircled by the dark energy through approximate Lie symmetries

We investigate the gravitational energy of the Reissner-Nordström black hole encircled by dark energy using the approach of approximate Lie symmetries of second-order. We confine our calculations to following values of the equation of state parameter ω: (i) (quintessence regime of dark energy), (ii) ω Λ = −1 (the pure cosmological constant regime), (iii) (frustrated cosmic strings network). In order to examine the gravitational energy for the Reissner-Nordström black hole spacetime encircled by the dark energy, we construct a system of second-order perturbed geodesic equations, which is done primarily by considering the mass M and charge Q of the black hole in terms of some small perturbation parameter ϵ. It is observed that we do not obtain any non-trivial approximate symmetry generator for any value of the state parameter ω, we get only trivial second-order approximate symmetry generators. As a result of these trivial approximate symmetries we get a rescaling of the proper time s which gives the rescaling of energy in the Reissner-Nordström spacetime encircled by the dark energy. It is found that for and ω Λ = −1, the rescaling factor for energy is dependent on r and for , the rescaling factor is independent of the radial distance r. Furthermore, we investigate that the effect of cosmological constant and quintessence dark energy decreases the energy of the underlying spacetime while the equation of state parameter , for which the Universe is static, increases the energy of the Reissner-Nordström black hole spacetime encircled by the dark energy.

Ehlers transformations as EM duality in the double copy

Given a solution to 4D Einstein gravity with an isometry direction, it is known that the equations of motion are identical to those of a 3D $\sigma$-model with target space geometry $SU(1,1)/U(1)$. Thus, any transformation by $SU(1, 1) \cong SL(2,\mathbb{R})$ is a symmetry for the action and allows one to generate new solutions in 4D. Here we clarify and extend recent work on electromagnetic (EM) duality in the context of the classical double copy. In particular, for pure gravity, we identify an explicit map between the Maxwell field of the single copy and the scalars in the target space, allowing us to identify the $U(1) \subset SL(2, \mathbb{R})$ symmetry dual to EM duality in the single copy. Moreover, we extend the analysis to Einstein-Maxwell theory, where we highlight the role of Ehlers-Harrison transformations and, for spherically symmetric charged black hole solutions, we interpret the equations of motion as a truncation of the putative single copy for Einstein-Yang-Mills theory.

Analytic treatment of near-extremal charged black holes supporting non-minimally coupled massless scalar clouds

It has recently been revealed that massless scalar fields which are non-minimally coupled to the Maxwell electromagnetic tensor can be supported in the exterior spacetime regions of spherically symmetric charged black holes. The boundary between scalarized charged black-hole spacetimes and bald (scalarless) Reissner–Nordström black holes is determined by the presence of a critical existence-line which describes spatially regular linearized scalar ‘clouds’ that are supported in the black-hole spacetime. In the present paper we use analytical techniques in order to solve the Klein–Gordon wave equation for the non-minimally coupled linearized scalar fields in the spacetimes of near-extremal supporting black holes. In particular, we derive a remarkably compact analytical formula for the discrete resonant spectrum {alpha (l,Q/M;n)}^{n=infty }_{n=1} which characterizes the dimensionless coupling parameter of the composed Reissner–Nordström-black-hole-nonminimally-coupled-massless-scalar-field configurations along the critical existence-line of the Einstein–Maxwell-scalar theory (here Q/M is the dimensionless charge-to-mass ratio of the central supporting black hole and l is the angular harmonic index of the supported scalar configurations).

The solution of a modified Hamilton–Jacobi equation with Lorentz-violating scalar field

A modified Hamilton–Jacobi equation with Lorentz-violating scalar field in the curved spacetime is used to research tunneling radiation from the horizons of Reissner–Nordstr $$\ddot{\mathrm{o}}$$ m de Sitter black hole. We investigate the influence of different etheric-like vector $$u^\alpha $$ on the solution of the modified Hamilton–Jacobi equation by using both the semi-classical approximation and beyond the semi-classical approximation. We find that the solution of the modified Hamilton–Jacobi equation strongly depends on the choices of $$u^\alpha $$ . As $$u^\alpha =\delta ^\alpha _t u^t$$ , the Lorentz-violating scalar field can enhances black holes’ Hawking temperature but reduces its entropy. However, the case will reverses as $$u^\alpha =\delta ^\alpha _r u^r$$ . Our conclusions are applicable to other spherically symmetric charged black holes.

The volume of quasi-static spherically symmetric charged black hole

Black holes that have evaporated are often thought of as small objects due to their tiny exterior area. However, the horizon bounds large spacelike hypersurfaces. A compelling geometric perspective on the evolution of the interior geometry was recently shown to be provided by a generally covariant definition of the volume inside a black hole using maximal surfaces. The case of an evaporating black hole has been illustrated. In this article, we expand on previous results in a different way and give a general method for solving the volume of a quasi-static spherically symmetric black hole. Our results are the same as before, while the area is shrinking, the volume of these surfaces grows monotonically with advanced time. However, the volume tends to be constant over time rather than proportional to time. The physical relevance of these results for the information paradox and the remnant scenarios is discussed.

Bounds on photon spheres and shadows of charged black holes in Einstein-Gauss-Bonnet-Maxwell gravity

We consider spherically symmetric and static charged black holes in Einstein-Gauss-Bonnet-Maxwell gravities in general D≥5 dimensions and study their photon spheres and black hole shadows. We show that they all satisfy the sequence of inequalities recently proposed relating a black hole's horizon, photon sphere, shadow and its mass.

Hayward black holes in Einstein–Gauss–Bonnet gravity

The Hayward metric is a spherically symmetric charged regular black holes, a modification of the Reisnner–Nordström black holes of Einstein’s equations coupled to nonlinear electrodynamics. We consider Einstein–Gauss–Bonnet gravity (EGB) coupled to nonlinear electrodynamics to present an exact five dimension (5D) Hayward black holes with a regular center, having inner (Cauchy) and outer (event) horizons which go over to Boulware–Desser black holes when the charge is switched off (e=0). The presence of charge e leads the modification in thermodynamical quantities, and it has also been shown that the Hawking–Page like phase transition can be achieved. The specific heat shows divergence at the horizon radius r=rC (critical radius), where the temperature has a maximum. Our result in the limit, e→0, reduces vis-a-vis to the 5D Boulware–Desser solutions.

Greybody factor and sparsity of Hawking radiation from a charged spherical black hole with scalar hair

The ‘no-hair’ conjecture claims that for a spherically symmetric black hole, only the information regarding the mass and charge of the black hole is available to an external observer. However, there are numerous counterexamples to the ‘no-hair’ conjecture. In this work, we consider a particular counter-example to the ‘no-hair’ conjecture in (3+1) dimensions, namely, a static spherically symmetric charged black hole with a scalar hair. We provide semi-analytic bounds on the greybody factors and study the sparsity of Hawking radiation of mass-less uncharged scalar fields. Our results show that the scalar and electric charges contribute oppositely to the greybody factor and the sparsity of the Hawking radiation cascade. Also, the greybody factor decreases and the Hawking emission spectra become more sparse with the reduction in the black hole (ADM) mass.