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.

Quantum radiation of Maxwell’s electromagnetic field in nonstationary Kerr–de Sitter black hole

2016 ◽  
Vol 25 (05) ◽  
pp. 1650061 ◽  
Author(s):  
T. Ibungochouba Singh ◽  
I. Ablu Meitei ◽  
K. Yugindro Singh
Keyword(s):  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Scalar Particle ◽  
De Sitter ◽  
Nonthermal Radiation ◽  
Thermal Radiation Spectrum ◽  
Quantum Radiation ◽  
Tortoise Coordinate ◽  
Generalized Tortoise Coordinate Transformation

Quantum radiation properties of nonstationary Kerr–de Sitter (KdS) black hole is investigated using the method of generalized tortoise coordinate transformation. The locations of horizons and the temperature of the thermal radiation as well as the maximum energy of the nonthermal radiation are derived. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Maxwell’s electromagnetic field equations which is absent in the thermal radiation spectrum of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the nonthermal radiation for KdS black hole. It is also shown that the generalized tortoise coordinate transformation produces a constant term in the expression of the surface gravity and Hawking temperature.

scholarly journals Quantum Radiation Properties of General Nonstationary Black Hole

2017 ◽  
Vol 2017 ◽  
pp. 1-15
Author(s):  
T. Ibungochouba Singh
Keyword(s):  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Scalar Particles ◽  
Dirac Equations ◽  
Quantum Radiation ◽  
Radiation Properties ◽  
Tortoise Coordinate ◽  
Generalized Tortoise Coordinate Transformation ◽  
Nonstationary Black Hole

Using the generalized tortoise coordinate transformations the quantum radiation properties of Klein-Gordon scalar particles, Maxwell’s electromagnetic field equations, and Dirac equations are investigated in general nonstationary black hole. The locations of the event horizon and the Hawking temperature depend on both time and angles. A new extra coupling effect is observed in the thermal radiation spectrum of Maxwell’s equations and Dirac equations which is absent in the thermal radiation spectrum of scalar particles. We also observe that the chemical potential derived from scalar particles is equal to the highest energy of the negative-energy state of the scalar particle in the nonthermal radiation in general nonstationary black hole. Applying generalized tortoise coordinate transformation a constant termξis produced in the expression of thermal radiation in general nonstationary black hole. It indicates that generalized tortoise coordinate transformation is more accurate and reliable in the study of thermal radiation of black hole.

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.

QUANTUM ERGOSPHERE AND HAWKING PROCESS

1999 ◽  
Vol 14 (28) ◽  
pp. 1951-1960 ◽  
Author(s):  
ZHONG-HENG LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermal Radiation ◽  
Radiation Spectrum ◽  
Spherically Symmetric ◽  
Field Equations ◽  
Stationary Black Hole ◽  
Symmetric Black Hole ◽  
Hawking Process ◽  
Nonstationary Black Hole

We study both spherically symmetric and rotating (Kerr) nonstationary black holes and discuss the radiation of these black holes via the Hawking process. We find that the thermal radiation spectrum of a nonstationary black hole is obviously dependent on the spin state of a particle and is different from the case of a stationary black hole. This effect originates from the quantum ergosphere. We also find that the field equations of spin s=0,1/2,1 and 2 can combine into a generalized Teukolsky-type master equation with sources for any spherically symmetric black hole.

scholarly journals Quantum Radiation Properties of Dirac Particles in General Nonstationary Black Holes

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jia-Chen Hua ◽  
Yong-Chang Huang
Keyword(s):  
Black Holes ◽  
Thermal Radiation ◽  
Event Horizon ◽  
Radiation Spectrum ◽  
Scalar Particles ◽  
Nonthermal Radiation ◽  
Dirac Particles ◽  
Thermal Radiation Spectrum ◽  
Quantum Radiation ◽  
Radiation Properties

Quantum radiation properties of Dirac particles in general nonstationary black holes in the general case are investigated by both using the method of generalized tortoise coordinate transformation and considering simultaneously the asymptotic behaviors of the first-order and second-order forms of Dirac equation near the event horizon. It is generally shown that the temperature and the shape of the event horizon of this kind of black holes depend on both the time and different angles. Further, we give a general expression of the new extra coupling effect in thermal radiation spectrum of Dirac particles which is absent from the thermal radiation spectrum of scalar particles. Also, we reveal a relationship that is ignored before between thermal radiation and nonthermal radiation in the case of scalar particles, which is that the chemical potential in thermal radiation spectrum is equal to the highest energy of the negative energy state of scalar particles in nonthermal radiation for general nonstationary black holes.

CHARACTERISTICS OF QUANTUM RADIATION OF SLOWLY VARYING NONSTATIONARY KERR–NEWMAN BLACK HOLES

2009 ◽  
Vol 24 (10) ◽  
pp. 1889-1899 ◽  
Author(s):  
JIA-CHEN HUA ◽  
YONG-CHANG HUANG
Keyword(s):  
Black Holes ◽  
Thermal Radiation ◽  
Chemical Potential ◽  
Energy State ◽  
Negative Energy ◽  
Nonthermal Radiation ◽  
Quantum Radiation ◽  
Tortoise Coordinate ◽  
Generalized Tortoise Coordinate Transformation ◽  
Radiative Characteristics

Quantum radiative characteristics of slowly varying nonstationary Kerr–Newman black holes are investigated by using the method of generalized tortoise coordinate transformation. It is shown that the temperature and the shape of the event horizon of this kind of black holes depend on the time and the angle. Further, we reveal a previously ignored relationship between thermal radiation and nonthermal radiation, which is that the chemical potential in the thermal radiation spectrum is equal to the highest energy of the negative energy state of particles in nonthermal radiation for slowly varying nonstationary Kerr–Newman black holes. Also, we show that the deduced general results can be degenerated to the known conclusion of stationary Kerr–Newman black holes.

scholarly journals Over-spinning Kerr–Sen black holes with test fields

2019 ◽  
Vol 28 (02) ◽  
pp. 1950044 ◽  
Author(s):  
Koray Düztaş
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gordon Equation ◽  
Naked Singularity ◽  
Weak Form ◽  
Scalar Fields ◽  
Cosmic Censorship ◽  
Extremal Black Hole ◽  
Klein Gordon ◽  
Fermionic Fields

In this work, we investigate validity of the weak form of the cosmic censorship conjecture in the interaction of Kerr–Sen black holes with neutral test fields. Previous studies of the Klein–Gordon equation on Kerr–Sen background imply that superradiance occurs for scalar fields. We show that scalar fields can overspin a nearly extremal black hole into a naked singularity, but the modes that could overspin an extremal black hole are not absorbed due to superradiance. From Kerr analogy one can naively expect superradiance to be absent for fermionic fields. In such a case overspinning becomes generic and also applies to extremal Kerr–Sen black holes. This robust violation of cosmic censorship cannot be fixed by backreaction effects which are ignored in this work. These results are analogous to the Kerr case.

scholarly journals Instability of charged massive scalar fields in bound states around Kerr–Sen black holes

2015 ◽  
Vol 24 (14) ◽  
pp. 1550102 ◽  
Author(s):  
Haryanto M. Siahaan
Keyword(s):  
Black Holes ◽  
Bound States ◽  
Gordon Equation ◽  
Scalar Fields ◽  
Bound State ◽  
Imaginary Component ◽  
Scalar Perturbation ◽  
Massive Scalar ◽  
Massive Scalar Field ◽  
Klein Gordon

In this paper, we show the instability of a charged massive scalar field in bound states around Kerr–Sen black holes. By matching the near and far region solutions of the radial part in the corresponding Klein–Gordon equation, one can show that the frequency of bound state scalar fields contains an imaginary component which gives rise to an amplification factor for the fields. Hence, the unstable modes for a charged and massive scalar perturbation in Kerr–Sen background can be shown.

scholarly journals Ten shades of black

2015 ◽  
Vol 24 (12) ◽  
pp. 1544007 ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Radiation Spectrum ◽  
Black Hole Physics ◽  
Black Body ◽  
Black Hole Radiation ◽  
Dimensional Spacetime ◽  
Opposite Behavior ◽  
Curvature Potential ◽  
Energy Dependent

The holographic principle has taught us that, as far as their entropy content is concerned, black holes in (3 + 1)-dimensional curved spacetimes behave as ordinary thermodynamic systems in flat (2 + 1)-dimensional spacetimes. In this paper, we point out that the opposite behavior can also be observed in black-hole physics. To show this we study the quantum Hawking evaporation of near-extremal Reissner–Nordström (RN) black holes. We first point out that the black-hole radiation spectrum departs from the familiar radiation spectrum of genuine (3 + 1)-dimensional perfect black-body emitters. In particular, the would be black-body thermal spectrum is distorted by the curvature potential which surrounds the black-hole and effectively blocks the emission of low-energy quanta. Taking into account the energy-dependent gray-body factors which quantify the imprint of passage of the emitted radiation quanta through the black-hole curvature potential, we reveal that the (3 + 1)-dimensional black holes effectively behave as perfect black-body emitters in a flat (9 + 1)-dimensional spacetime.

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.

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