Black Hole Absorption Research Articles

Greybody factors, quasi-normal modes and thermal fluctuations of quantum-corrected Schwarzschild black hole surrounded by quintessence

In this study, we examine the effects of a quintessence field-enclosed Schwarzschild black hole that has undergone quantum corrections on a number of different physical phenomena. The effective potential and its graphical features across different values of the quantum correction and quintessence field as well as relevant physical parameters are analyzed by deriving the radial equation from the Klein–Gordon equation and converting it into a Schrodinger wave equation using the tortoise coordinate. Both the event and cosmic horizons are found in the solutions to the radial equation. We provide a detailed analysis of the greybody component and its behavior by merging these solutions in the intermediate regime. By analyzing the black hole metric function, effective potential, and absorption probabilities, the study uncovers the complex relationship between black hole characteristics, quantum corrections, and the surrounding quintessence field. Investigating the BH’s quasinormal modes and thermal fluctuations provides insights into its stability as well as thermodynamic properties. The findings offer a comprehensive understanding of how the black hole interacts with its environment and responds to environmental changes, shedding light on the rich dynamics of black hole systems in the presence of quantum corrections and quintessence fields.

Soft black hole absorption rates as conservation laws

The absorption rate of low-energy, or soft, electromagnetic radiation by spherically symmetric black holes in arbitrary dimensions is shown to be fixed by conservation of energy and large gauge transformations. We interpret this result as the explicit realization of the Hawking-Perry-Strominger Ward identity for large gauge transformations in the background of a non-evaporating black hole. Along the way we rederive and extend previous analytic results regarding the absorption rate for the minimal scalar and the photon.

Semiclassical approach to black hole absorption of electromagnetic radiation emitted by a rotating charge

We consider an electric charge, minimally coupled to the Maxwell field, rotating around a Schwarzschild black hole. We investigate how much of the radiation emitted from the swirling charge is absorbed by the black hole and show that most of the photons escape to infinity. For this purpose we use the Gupta-Bleuler quantization of the electromagnetic field in the modified Feynman gauge developed in the context of quantum field theory in Schwarzschild spacetime. We obtain that the two photon polarizations contribute quite differently to the emitted power. In addition, we discuss the accurateness of the results obtained in a full general relativistic approach in comparison with the ones obtained when the electric charge is assumed to be orbiting a massive object due to a Newtonian force.

Gravitational waveforms from a point particle orbiting a Schwarzschild black hole

We numerically solve the inhomogeneous Zerilli-Moncrief and Regge-Wheeler equations in the time domain. We obtain the gravitational waveforms produced by a point-particle of mass $\mu$ traveling around a Schwarzschild black hole of mass M on arbitrary bound and unbound orbits. Fluxes of energy and angular momentum at infinity and the event horizon are also calculated. Results for circular orbits, selected cases of eccentric orbits, and parabolic orbits are presented. The numerical results from the time-domain code indicate that, for all three types of orbital motion, black hole absorption contributes less than 1% of the total flux, so long as the orbital radius r_p(t) satisfies r_p(t)> 5M at all times.

Metric of the multiply wound rotating string

We consider a string wrapped many times around a compact circle in space, and let this string carry a right-moving wave which imparts momentum and angular momentum to the string. The angular momentum causes the strands of the ‘multiwound’ string to separate and cover the surface of a torus. We compute the supergravity solution for this string configuration. We map this solution by dualities to the D1–D5 system with angular momentum that has been recently studied. We discuss how constructing this multiwound string solution may help us to relate the microscopic and macroscopic pictures of black hole absorption.

Post-Newtonian Expansion of Gravitational Waves from a Particle in Circular Orbits around a Rotating Black Hole: Effects of Black Hole Absorption

Coalescing compact binaries are the most promising candidates for detection by near-future, ground based laser interferometric detectors. It is very important to investigate detailed wave forms from coalescing compact binaries. When one (or two) of the stars is a black hole, some of those waves are absorbed by the black hole. Here, we consider a case when a test particle moves circular orbit on the equatorial plane around a Kerr black hole, and calculate the the energy absorption rate by the black hole. We adopt an analytic techniques for the Teukolsky equation which was found by Mano, Suzuki, and Takasugi (1996). We calculated the energy absorption rate to O((v/c)13) beyond the Newtonian-quadrupole formula of gravitational waves radiated to infinity, assuming v/c ≪ 1. Here v is the velocity of the particle. We find that, when a black hole is rotating, the black hole absorption appear at O((v/c)5) beyond the Newtonian-quadrapole formula. These effects become more important as the mass of the black hole becomes larger. We also found that the black hole absorption is more important when a particle moves to the same direction of the black hole rotation. All the details of this paper is presented in Tagoshi et al. (1997).

Black hole absorption cross-sections and the anti-de Sitter–conformal field theory correspondence

Recent work has uncovered a correspondence between theories in anti-de Sitter space, and those on its boundary. This has important implications for black holes in string theory which have near-horizon AdS geometries. Using the effective coupling to the boundary conformal field theory, I compute the low-energy, s-wave absorption cross-sections for a minimally coupled scalar in the near-extremal four- and five-dimensional black holes. The results agree precisely with semi-classical gravity calculations. Agreement for fixed scalars, and for the BTZ black hole, is also found.

Post-Newtonian Expansion of Gravitational Waves from a Particle in Circular Orbits around a Rotating Black Hole: Effects of Black Hole Absorption

When a particle moves around a Kerr black hole, it radiates gravitational waves.Some of these waves are absorbed by the black hole. We calculate such absorption of gravitational waves induced by a particle of mass mu in a circular orbit on an equatorial plane around a Kerr black hole of mass M. We assume that the velocity of the particle v is much smaller than the speed of light c and calculate the energy absorption rate analytically. We adopt an analytic technique for the Teukolsky equation developed by Mano, Suzuki and Takasugi. We obtain the energy absorption rate to O((v/c)^8) compared to the lowest order. We find that the black hole absorption occurs at O((v/c)^5) beyond the Newtonian-quadrapole luminosity at infinity in the case when the black hole is rotating, which is O((v/c)^3) lower than the non-rotating case. Using the energy absorption rate, we investigate its effects on the orbital evolution of coalescing compact binaries.

Black hole greybody factors and absorption of scalars by effective strings

We compute the greybody factors for classical black holes in a domain where two kinds of charges and their anticharges are excited by the extra energy over extremality. We compare the result to the greybody factors expected from an effective string mode] which was earlier shown to give the correct entropy. In the regime where the left- and right-moving temperatures are much smaller than the square root of the effective string tension, we find a non-trivial greybody factor which agrees with the effective string mode]. However, if the temperatures are comparable with the square root of the effective string tension, the greybody factors agree only at the leading order in energy. Nevertheless, there are several interesting relations between the two results, suggesting that a modification of the effective string mode] might lead to better agreement.

Gravitational radiation from a particle in circular orbit around a black hole. V. Black-hole absorption and tail corrections.

A particle of mass \ensuremath{\mu} moves on a circular orbit of a nonrotating black hole of mass M. Under the restrictions \ensuremath{\mu}/M\ensuremath{\ll}1 and v\ensuremath{\ll}1, where v is the orbital veloity (in units in which c=1), we consider the gravitational waves emitted by such a binary system. The framework is that of black-hole perturbation theory. We calculate E\ifmmode \dot{}\else \.{}\fi{}, the rate at which the gravitational waves remove energy from the system. The total energy loss is given by E\ifmmode \dot{}\else \.{}\fi{}=E\ifmmode \dot{}\else \.{}\fi{} $^{\mathrm{\ensuremath{\infty}}}$+E\ifmmode \dot{}\else \.{}\fi{} $^{\mathit{H}}$, where E\ifmmode \dot{}\else \.{}\fi{} $^{\mathrm{\ensuremath{\infty}}}$ denotes that part of the gravitational-wave energy which is carried off to infinity, while E\ifmmode \dot{}\else \.{}\fi{} $^{\mathit{H}}$ denotes the part which is absorbed by the black hole. We show that the black-hole absorption is a small effect: E\ifmmode \dot{}\else \.{}\fi{} $^{\mathit{H}}$/E\ifmmode \dot{}\else \.{}\fi{}\ensuremath{\simeq}${\mathit{v}}^{8}$. This is explained by the presence of a potential barrier in the vicinity of the black hole: Most of the waves propagating initially toward the black hole are reflected off the barrier; the black hole is therefore unable to absorb much. The black-hole absorption, and indeed any other effect resulting from imposing ingoing-wave boundary conditions at the event horizon, are sufficiently small to be irrelevant to the construction of matched filters for gravitational-wave measurements. To derive this result we extend the techniques previously developed by Poisson and Sasaki for integrating the Regge-Wheeler equation. The extension consists of an explicit consideration of the horizon boundary conditions, which were largely ignored in the previous work. Finally, we compare the wave generation formalism which derives from perturbation theory to the post-Newtonian formalism of Blanchet and Damour. Among other things we consider the corrections to the asymptotic gravitational-wave field which are due to wave-propagation (tail) effects. The results obtained using perturbation theory are identical to that of post-Newtonian theory.

Matter-antimatter accounting, thermodynamics, and black-hole radiation

We discuss several issues bearing on the observed asymmetry between matter and antimatter in the content of the universe, in particular, the possible role in this of Hawking radiation from black holes, with allowance for weak $C$- and $T$-violating interactions. We show that the radiation, species by species, can be asymmetric between baryons and antibaryons. However, if baryon number is microscopically conserved there cannot be a net flux of baryon number in the radiation. Black-hole absorption from a medium with net baryon number zero can drive the medium to an asymmetric state. On the other hand, if baryon conservation is violated, a net asymmetry can develop. This can arise through asymmetric gravitational interactions of the radiated particles, and conceivably, by radiation of long-lived particles which decay asymmetrically. In the absence of microscopic baryon conservation, asymmetries can also arise from collision processes generally, say in the early stages of the universe as a whole. However, no asymmetries can develop (indeed any initial ones are erased) insofar as the baryon-violating interactions are in thermal equilibrium, as they might well be in the dense, high-temperature stages of the very early universe. Thus particle collisions can generate asymmetries only when nonequilibrium effects driven by cosmological expansion come into play. A scenario for baryon-number generation suggested by superunified theories is discussed in some detail. Black-hole radiation is another highly nonequilibrium process which is very efficient in producing asymmetry, given microscopic $C$, $T$, and baryon-number violation.