scholarly journals Greybody factor for a rotating black hole with quintessential energy

2020 ◽  
Vol 2020 (3) ◽  
Author(s):  
M Sharif ◽  
Qanitah Ama-Tul-Mughani
Keyword(s):  
Black Hole ◽  
Effective Potential ◽  
State Parameter ◽  
Scalar Fields ◽  
Accelerated Expansion ◽  
Massless Scalar ◽  
Emission Rates ◽  
Rotating Black Hole ◽  
Klein Gordon ◽  
Tortoise Coordinate

Abstract This paper is devoted to deriving an analytic expression of the greybody factor for a rotating black hole surrounded by quintessence. Primarily, we transform the radial part of the Klein–Gordon equation into the standard Schrödinger equation through the tortoise coordinate to analyze the profile of the effective potential. Asymptotic solutions are obtained in two distinct regions, namely, the black hole and cosmological horizons determined by the quintessential field. We then extrapolate these solutions and match them smoothly in an intermediate region to extend the viability over the whole radial regime. To elaborate the significance of the analytical solution, we evaluate the emission rates and absorption cross-section for the massless scalar fields. It is found that the accelerated expansion of the universe corresponding to smaller values of the state parameter minimizes the effective potential and consequently increases the emission process of the scalar field particles.

Joule–Thomson expansion and quasinormal modes of regular non-minimal magnetic black hole

2020 ◽  
Vol 35 (36) ◽  
pp. 2050298
Author(s):  
Abdul Jawad ◽  
Muhammad Yasir ◽  
Shamaila Rani
Keyword(s):  
Black Hole ◽  
Mass Formula ◽  
Quasinormal Modes ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Thomson Effect ◽  
First Order ◽  
Thermodynamical Parameters ◽  
Klein Gordon ◽  
Tortoise Coordinate

The Joule–Thomson effect and quasinormal modes (QNM) onto regular non-minimal magnetic charged black hole with a cosmological constant are being investigated. For this purpose, we extract some thermodynamical parameters such as pressure [Formula: see text] and mass [Formula: see text] in the presence of magnetic [Formula: see text] as well as electric [Formula: see text] charge. These parameters lead to inversion temperature [Formula: see text], pressure [Formula: see text] and corresponding isenthalpic curves. We introduce the tortoise coordinate and the Klein–Gordon wave equation which leads to the second-order ordinary Schrödinger equation. We find out the complex frequencies of QNMs through the massless scalar field perturbation which satisfy boundary conditions by using the first-order Wentzel–Kramers–Brillouin (WKB) technique.

scholarly journals NON-EXISTENCE OF NEW QUANTUM ERGOSPHERE EFFECT OF A VAIDYA-TYPE BLACK HOLE

2001 ◽  
Vol 16 (24) ◽  
pp. 1549-1557 ◽  
Author(s):  
S. Q. WU ◽  
X. CAI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Scalar Fields ◽  
Dirac Particles ◽  
Klein Gordon ◽  
Tortoise Coordinate ◽  
Generalized Tortoise Coordinate Transformation ◽  
Spherically Symmetry

Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type black hole is investigated by the method of generalized tortoise coordinate transformation. It is shown that Hawking radiation of Dirac particles does not exist for P1, Q2 components but for P2, Q1 components in any Vaidya-type black holes. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein–Gordon particles. We demonstrate that there is no new quantum ergosphere effect in the thermal radiation of Dirac particles in any spherically symmetry black holes.

scholarly journals Failure of mean-field approximation in weakly coupled dilaton gravity

2018 ◽  
Vol 191 ◽  
pp. 07004
Author(s):  
Maxim Fitkevich
Keyword(s):  
Black Hole ◽  
Mean Field ◽  
Direct Calculation ◽  
Scalar Fields ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Massless Scalar ◽  
Dilaton Gravity ◽  
Black Hole Evaporation ◽  
Weakly Coupled

We investigate black hole evaporation in a weakly coupled model of two-dimensional dilaton gravity paying a particular attention to the validity of the semiclassical mean-field approximation. Our model is obtained by adding a reflecting boundary to the celebrated RST model describing N gravitating massless scalar fields to one-loop level. The boundary cuts off the region of strong coupling. Although our model is explicitly weakly coupled, we find that the mean field approximation inevitably fails at the end of black hole evaporation. We propose an alternative semiclassical method aiming at direct calculation of S-matrix elements and illustrate it in a simple shell model.

scholarly journals PASSAGE OF RADIATION THROUGH WORMHOLES

2009 ◽  
Vol 18 (11) ◽  
pp. 1665-1691 ◽  
Author(s):  
ANDREY DOROSHKEVICH ◽  
JAKOB HANSEN ◽  
IGOR NOVIKOV ◽  
ALEXANDER SHATSKIY
Keyword(s):  
Black Hole ◽  
Scalar Fields ◽  
Radiation Pulse ◽  
Massless Scalar ◽  
Subsequent Evolution ◽  
Gravitational Action ◽  
Zero Mass ◽  
Symmetrical Solution

We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by a spherically symmetrical solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and investigate the dynamics of the fields in this process for both cases: collapse of the wormhole into the black hole and for the expanding wormhole.

scholarly journals THE TWO-DIMENSIONAL STRINGY BLACK HOLE: A NEW APPROACH AND A NEW EFFECT

1996 ◽  
Vol 11 (08) ◽  
pp. 1463-1488
Author(s):  
H.J. DE VEGA ◽  
J. RAMÍREZ MITTELBRUN ◽  
M. RAMÓN MEDRANO ◽  
N. SÁNCHEZ
Keyword(s):  
Black Hole ◽  
Physical Phenomenon ◽  
Type Equation ◽  
Scalar Particle ◽  
Conformal Anomaly ◽  
Massless Scalar ◽  
Two Dimensional ◽  
New Approach ◽  
Klein Gordon ◽  
String Propagation

The string propagation in the two-dimensional stringy black hole is investigated from a new approach. We completely solve the classical and quantum string dynamics in the Lorentzian and Euclidean regimes. In the Lorentzian case all the physics reduces to a massless scalar particle described by a Klein-Gordon type equation with a singular effective potential. The scattering matrix is found and it reproduces the results obtained by coset CFT techniques. It factorizes into two pieces: an elastic Coulombian amplitude and an absorption part. In both parts, an infinite sequence of imaginary poles in the energy appears. The generic features of string propagation in curved D-dimensional backgrounds (string stretching, fall into space-time singularities) are analyzed in the present case. A new physical phenomenon specific to the present black hole is found: the quantum renormalization of the speed of light. We find that [Formula: see text] where k is the integer in front of the WZW action. Only for k→∞ does this new effect disappear (although the conformal anomaly is present). We analyze all the classical Euclidean string solutions and exactly compute the quantum partition function. No critical Hagedorn temperature appears here.

scholarly journals Trajectory around a spherically symmetric non-rotating black hole

2011 ◽  
Vol 89 (6) ◽  
pp. 689-695 ◽  
Author(s):  
Sumanta Chakraborty ◽  
Subenoy Chakraborty
Keyword(s):  
Black Hole ◽  
Gravitational Field ◽  
Gravitational Potential ◽  
Test Particle ◽  
Effective Potential ◽  
Particle Motion ◽  
Spherically Symmetric ◽  
Rotating Black Hole

The trajectory of a test particle or a photon around a general spherical black hole is studied, and bending of the light trajectory is investigated. A pseudo-Newtonian gravitational potential describing the gravitational field of the black hole is determined and is compared with the related effective potential for test particle motion. As an example, results are presented for a Reissner–Nordström black hole.

Stationary bound states of massless scalar fields around black holes and black hole analogues

2015 ◽  
Vol 24 (09) ◽  
pp. 1542018 ◽  
Author(s):  
Carolina L. Benone ◽  
Luís C. B. Crispino ◽  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Distribution ◽  
Scalar Field ◽  
Bound States ◽  
Neumann Boundary ◽  
Mass Term ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Field System

We discuss stationary bound states, a.k.a. clouds, for a massless test scalar field around Kerr black holes (BHs) and spinning acoustic BH analogues. In view of the absence of a mass term, the trapping is achieved via enclosing the BH — scalar field system in a cavity and imposing Dirichlet or Neumann boundary conditions. We discuss the variation of these bounds states with the discrete parameters that label them, as well as their spatial distribution, complementing results in our previous work [C. L. Benone, L. C. B. Crispino, C. Herdeiro and E. Radu, Phys. Rev. D91 (2015) 104038].

scholarly journals Scalar waves in regular Bardeen black holes: Scattering, absorption and quasinormal modes

2016 ◽  
Vol 25 (09) ◽  
pp. 1641008 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luís C. B. Crispino ◽  
Ednilton S. de Oliveira
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Quasinormal Modes ◽  
Scalar Fields ◽  
Scattering Cross Section ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Scattering Cross

We discuss the phenomenology of massless scalar fields around a regular Bardeen black hole, namely absorption cross-section, scattering cross-section and quasinormal modes. We compare the Bardeen and Reissner–Nordström black holes, showing limiting cases for which their properties are similar.

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

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Coupling Parameter ◽  
Analytical Formula ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Charged Black Holes ◽  
Black Hole Spacetimes ◽  
Electromagnetic Tensor

AbstractIt 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 $$\{\alpha (l,Q/M;n)\}^{n=\infty }_{n=1}$$ { α ( l , Q / M ; n ) } n = 1 n = ∞ 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).

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