scholarly journals On-axis scalar absorption cross section of Kerr–Newman black holes: Geodesic analysis, sinc and low-frequency approximations

2018 ◽  
Vol 27 (11) ◽  
pp. 1843012 ◽  
Author(s):  
Carolina L. Benone ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino ◽  
Sam R. Dolan
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Rotation Axis ◽  
Low Frequency ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Absorption Cross ◽  
Newman Black Hole

We investigate null geodesics impinging parallel to the rotation axis of a Kerr–Newman black hole, and show that the absorption cross section for a massless scalar field in the eikonal limit can be described in terms of the photon orbit parameters. We compare our sinc and low-frequency approximations with numerical results, showing that they are in excellent agreement.

scholarly journals Absorption by stringy black holes

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Sérgio V. M. C. B. Xavier ◽  
Carolina L. Benone ◽  
Luís C. B. Crispino
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Charged Black Holes ◽  
Hole Charge ◽  
Newman Black Hole ◽  
The Difference

AbstractWe investigate the absorption of planar massless scalar waves by a charged rotating stringy black hole, namely a Kerr–Sen black hole. We compute numerically the absorption cross section and compare our results with those of the Kerr–Newman black hole, a classical general relativity solution. In order to better compare both charged black holes, we define the ratio of the black hole charge to the extreme charge as Q. We conclude that Kerr–Sen and Kerr–Newman black holes have a similar absorption cross section, with the difference increasing for higher values of Q.

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.

HIDDEN CONFORMAL SYMMETRY OF ROTATING NS5-BRANES

2011 ◽  
Vol 26 (07n08) ◽  
pp. 1389-1398 ◽  
Author(s):  
M. R. SETARE ◽  
V. KAMALI
Keyword(s):  
Wave Equation ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Conformal Symmetry ◽  
Low Frequency ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Absorption Cross ◽  
Frequency Limit ◽  
Cardy Formula

In the present paper, we show that for a low frequency limit the wave equation of massless scalar field in the background of rotating NS5-branes can be written as the Casimir of SL (2, R) symmetry. Our result shows that the entropy of the rotating NS5-brane is reproduced by the Cardy formula, also the absorption cross-section is in consistence with the finite temperature absorption cross-section for a 2D CFT.

scholarly journals Absorption and Scattering Cross Section of Regular Black Holes

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hai Huang ◽  
Ping Liao ◽  
Juhua Chen ◽  
Yongjiu Wang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
High Frequency ◽  
Massless Scalar ◽  
Absorption Cross ◽  
High Frequency Region ◽  
Regular Black Hole ◽  
Regular Black Holes

By using the partial wave method, we investigate the absorption of massless scalar wave from regular black hole. We numerically carry out the absorption cross section and find that the larger angular momentum quantum number l is, the smaller the corresponding maximum value of partial absorption cross section is. Comparing with Schwarzschild case, the absorption cross section of regular black holes is strengthened in both low and high frequency regions, and the absorption cross section oscillates around the geometric optical value in the high frequency region. Generally speaking, the scattering flux is strengthened and its scattering width becomes narrower in the forward direction. There are obvious contrast of scattering properties of different type of regular black hole.

Absorption of massless scalar field by rotating black holes

2016 ◽  
Vol 25 (09) ◽  
pp. 1641024 ◽  
Author(s):  
Luiz C. S. Leite ◽  
Luís C. B. Crispino ◽  
Ednilton S. de Oliveira ◽  
Caio F. B. Macedo ◽  
Sam R. Dolan
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Cross Section ◽  
Absorption Cross Section ◽  
High Frequency ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Absorption Cross ◽  
Frequency Regime ◽  
Selection Of

We compute the absorption cross-section of the Kerr black holes (BH) for the massless scalar field, and present a selection of numerical results, to complement the results of Ref.[C. F. B. Macedo, L. C. S. Leite, E. S. Oliveria, S. R. Dolan and L. C. B. Crispino, Phys. Rev. D 88 (2013) 064033.] We show that, in the high-frequency regime, the cross-section approaches the geodesic capture cross-section. We split the absorption cross-section into corotating and counterrotating contributions, and we show that the counterrotating contribution exceeds the corotating one.

Absorption of zero-mass planar waves by dirty black holes

2018 ◽  
Vol 27 (11) ◽  
pp. 1843017 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino
Keyword(s):  
Black Holes ◽  
Cross Section ◽  
Accretion Disks ◽  
Absorption Cross Section ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Thin Spherical Shell ◽  
Nonlinear Nature ◽  
Selection Of

Astrophysical black holes are often with companions, including other gravitating objects, accretion disks, electromagnetic fields, and others. Because of the nonlinear nature of general relativity, it is difficult to account for the gravitational effects of these companions, which can only be investigated analytically for very few cases. In this paper, we consider black holes with surrounding matter — often called dirty black holes — and analyze the absorption cross section of massless scalar fields. We start by laying out the generic setup for spherically symmetric scenarios and then specify for a simple model. We consider planar massless scalar waves impinging upon a Schwarzschild black hole surrounded by a thin spherical shell, and compute the absorption cross section. We present a selection of numerical results complementary to those presented in [C. F. B. Macedo, L. C. S. Leite and L. C. B. Crispino, Phys. Rev. D 93 (2016) 024027, arXiv:1511.08781 [gr-qc]] for arbitrary frequencies, considering different values of the shell position as well as its mass.

scholarly journals On the temperature dependence of the absorption cross-section for black holes in string theory

2015 ◽  
Vol 24 (09) ◽  
pp. 1542011 ◽  
Author(s):  
Filipe Moura
Keyword(s):  
Black Holes ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Low Frequency ◽  
Spherically Symmetric ◽  
Absorption Cross ◽  
Explicit Dependence ◽  
Superstring Theory ◽  
Classical Level ◽  
Extremal Limit

We study the low frequency absorption cross-section of spherically symmetric nonextremal d-dimensional black holes. In the presence of α′ corrections, this quantity must have an explicit dependence on the Hawking temperature of the form 1/TH. This property of the low frequency absorption cross-section is shared by the D1-D5 system from type IIB superstring theory already at the classical level, without α′ corrections. We apply our formula to the simplest example, the classical d-dimensional Reissner–Nordström solution, checking that the obtained formula for the cross-section has a smooth extremal limit. We also apply it for a d-dimensional Tangherlini-like solution with α′3 corrections.

scholarly journals COMMENTS ON ABSORPTION CROSS-SECTION FOR CHERN–SIMONS BLACK HOLES IN FIVE DIMENSIONS

2011 ◽  
Vol 26 (23) ◽  
pp. 3997-4008 ◽  
Author(s):  
P. A. GONZÁLEZ ◽  
JOEL SAAVEDRA
Keyword(s):  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Low Frequency ◽  
Absorption Cross ◽  
Black Hole Mass ◽  
Frequency Limit ◽  
Massive Scalar Field ◽  
Five Dimensions ◽  
Chern Simons

In this paper we study the effects of black hole mass on the absorption cross-section for a massive scalar field propagating in a five-dimensional topological Chern–Simons black hole at the low-frequency limit. We consider the two branches of black hole solutions (α = ±1) and we show that, if the mass of black hole increase the absorption cross-section decreases at the zero-frequency limit for the branch α = -1 and for the other branch, α = 1, the behavior is opposite, if the black hole mass increase the absorption cross-section increases. Also we find that beyond a certain frequency value, the mass black hole does not affect the absorption cross-section.

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