scholarly journals Synchrotron radiation from a weakly magnetized Schwarzschild black hole

2015 ◽  
Vol 92 (12) ◽  
Author(s):  
Andrey A. Shoom
Keyword(s):  
Black Hole ◽  
Synchrotron Radiation ◽  
Schwarzschild Black Hole

Gravitational synchrotron radiation in the metric of a new theory of gravitation

1980 ◽  
Vol 58 (11) ◽  
pp. 1595-1598 ◽  
Author(s):  
R. B. Mann ◽  
J. W. Moffat
Keyword(s):  
Black Hole ◽  
Wave Equation ◽  
Synchrotron Radiation ◽  
Gravitational Radiation ◽  
Field Structure ◽  
Astrophysical Object ◽  
Schwarzschild Black Hole ◽  
Null Surface ◽  
Strong Source ◽  
Theory Of Gravitation

The wave equation for a scalar field ψ is solved in the background metric of a new theory of gravity, based on a non-Riemannian field structure with a nonsymmetric Hermitian gμν. In contrast to the solution of the problem in a Schwarzschild background metric, in which only orbits close to r ~ 3M yield significant gravitational radiation, the new metric leads to an effective potential with stable orbits for a substantial range of r. The solution yields ψ = (1 − ℓ4/r4)−1/2ψGR where ℓ is a new integration constant. The null surface r = ℓ determines an astrophysical object called a "deflectar", which for ℓ > 2M conceals the Schwarzschild black-hole event horizon at r = 2M. As r → ℓ the gravitational synchrotron radiation increases to infinity. The actual power output of gravitational radiation for physically allowed stable orbits closest to r = ℓ is estimated, demonstrating that a deflectar is a potentially strong source of gravitational radiation.

The Schwarzschild black hole

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Black Hole ◽  
Gravitational Field ◽  
Equilibrium Configuration ◽  
Original Form ◽  
Schwarzschild Black Hole ◽  
Schwarzschild Metric ◽  
Schwarzschild Geometry

This chapter discusses the Schwarzschild black hole. It demonstrates how, by a judicious change of coordinates, it is possible to eliminate the singularity of the Schwarzschild metric and reveal a spacetime that is much larger, like that of a black hole. At the end of its thermonuclear evolution, a star collapses and, if it is sufficiently massive, does not become stabilized in a new equilibrium configuration. The Schwarzschild geometry must therefore represent the gravitational field of such an object up to r = 0. This being said, the Schwarzschild metric in its original form is singular, not only at r = 0 where the curvature diverges, but also at r = 2m, a surface which is crossed by geodesics.

scholarly journals Black hole S-matrix for a scalar field

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Panos Betzios ◽  
Nava Gaddam ◽  
Olga Papadoulaki
Keyword(s):  
Black Hole ◽  
Normal Modes ◽  
Massless Scalar ◽  
Scattering Process ◽  
Schwarzschild Black Hole ◽  
Asymptotically Flat ◽  
Scalar Particles ◽  
Black Hole Background ◽  
S Matrix ◽  
Do So

Abstract We describe a unitary scattering process, as observed from spatial infinity, of massless scalar particles on an asymptotically flat Schwarzschild black hole background. In order to do so, we split the problem in two different regimes governing the dynamics of the scattering process. The first describes the evolution of the modes in the region away from the horizon and can be analysed in terms of the effective Regge-Wheeler potential. In the near horizon region, where the Regge-Wheeler potential becomes insignificant, the WKB geometric optics approximation of Hawking’s is replaced by the near-horizon gravitational scattering matrix that captures non-perturbative soft graviton exchanges near the horizon. We perform an appropriate matching for the scattering solutions of these two dynamical problems and compute the resulting Bogoliubov relations, that combines both dynamics. This allows us to formulate an S-matrix for the scattering process that is manifestly unitary. We discuss the analogue of the (quasi)-normal modes in this setup and the emergence of gravitational echoes that follow an original burst of radiation as the excited black hole relaxes to equilibrium.

scholarly journals Null Geodesics and Strong Field Gravitational Lensing in a String Cloud Background

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Galactic Center ◽  
Deflection Angle ◽  
Orbital Motion ◽  
Strong Field ◽  
Schwarzschild Black Hole ◽  
Field Limit ◽  
Null Geodesics ◽  
Supermassive Black Hole

This paper is devoted to studying two interesting issues of a black hole with string cloud background. Firstly, we investigate null geodesics and find unstable orbital motion of particles. Secondly, we calculate deflection angle in strong field limit. We then find positions, magnifications, and observables of relativistic images for supermassive black hole at the galactic center. We conclude that string parameter highly affects the lensing process and results turn out to be quite different from the Schwarzschild black hole.

scholarly journals GEODESIC STRUCTURE OF THE SCHWARZSCHILD BLACK HOLE IN RAINBOW GRAVITY

2009 ◽  
Vol 24 (18) ◽  
pp. 1443-1451 ◽  
Author(s):  
CARLOS LEIVA ◽  
JOEL SAAVEDRA ◽  
JOSÉ VILLANUEVA
Keyword(s):  
Black Hole ◽  
Test Particle ◽  
Radial Motion ◽  
Schwarzschild Black Hole ◽  
Geodesic Structure

In this paper we study the geodesic structure of the Schwarzschild black hole in rainbow gravity analyzing the behavior of null and time-like geodesic. We find that the structure of the geodesics essentially does not change when the semiclassical effects are included. However, we can distinguish different scenarios if we take into account the effects of rainbow gravity. Depending on the type of rainbow functions under consideration, inertial and external observers see very different situations in radial and non-radial motion of a test particle.

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