scholarly journals Casimir effect in free fall towards a Schwarzschild black hole

2019 ◽  
Vol 100 (10) ◽  
Author(s):  
Francesco Sorge ◽  
Justin H. Wilson
Keyword(s):  
Black Hole ◽  
Casimir Effect ◽  
Free Fall ◽  
Schwarzschild Black Hole

scholarly journals Local free-fall temperature of modified Schwarzschild black hole in rainbow spacetime

2016 ◽  
Vol 31 (17) ◽  
pp. 1650106 ◽  
Author(s):  
Yong-Wan Kim ◽  
Young-Jai Park
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Test Particle ◽  
Free Fall ◽  
Local Temperature ◽  
Schwarzschild Black Hole ◽  
Energy Formula ◽  
Fall Temperature ◽  
Flat Embedding

We obtain a (5+1)-dimensional global flat embedding of modified Schwarzschild black hole in rainbow gravity. We show that local free-fall temperature in rainbow gravity, which depends on different energy [Formula: see text] of a test particle, is finite at the event horizon for a freely falling observer, while local temperature is divergent at the event horizon for a fiducial observer. Moreover, these temperatures in rainbow gravity satisfy similar relations to those of the Schwarzschild black hole except the overall factor [Formula: see text], which plays a key role of rainbow functions in this embedding approach.

scholarly journals Something special at the event horizon

2014 ◽  
Vol 29 (40) ◽  
pp. 1450215 ◽  
Author(s):  
Myungseok Eune ◽  
Yongwan Gim ◽  
Wontae Kim
Keyword(s):  
Black Hole ◽  
Energy Density ◽  
Free Fall ◽  
Scalar Fields ◽  
Negative Energy ◽  
Two Dimensional ◽  
Schwarzschild Black Hole ◽  
Negative Energy Density ◽  
Trace Anomaly ◽  
Physical Consequences

We revisit the free-fall energy density of scalar fields semiclassically by employing the trace anomaly on a two-dimensional Schwarzschild black hole with respect to various black hole states in order to clarify whether something special at the horizon happens or not. For the Boulware state, the energy density at the horizon is always negative divergent, which is independent of initial free-fall positions. However, in the Unruh state the initial free-fall position is responsible for the energy density at the horizon and there is a critical point to determine the sign of the energy density at the horizon. In particular, a huge negative energy density appears when the freely falling observer is dropped just near the horizon. For the Hartle–Hawking state, it may also be positive or negative depending on the initial free-fall position, but it is always finite. Finally, we discuss physical consequences of these calculations.

scholarly journals Free-fall energy density and flux in the Schwarzschild black hole

2015 ◽  
Vol 30 (11) ◽  
pp. 1550053 ◽  
Author(s):  
Wontae Kim ◽  
Bibhas Ranjan Majhi
Keyword(s):  
Black Hole ◽  
Energy Density ◽  
Free Fall ◽  
Negative Energy ◽  
Schwarzschild Black Hole ◽  
Spatial Infinity ◽  
Negative Energy Density ◽  
Conformally Invariant ◽  
Trace Anomaly

In the four-dimensional background of Schwarzschild black hole, we investigate the energy densities and fluxes in the freely falling frames for the Boulware, Unruh, and Israel–Hartle–Hawking states. In particular, we study their behaviors near the horizon and asymptotic spatial infinity by using the trace anomaly of a conformally invariant scalar field. In the Boulware state, both the energy density and flux are negative divergent when the observer is dropped at the horizon, and asymptotically vanish. In the Unruh state, the energy density is also negative divergent at the horizon while it is positive finite asymptotically. The flux in the Unruh state is always positive and divergent at the horizon. In the Israel–Hartle–Hawking state, the energy density depends on the angular motion of free fall, and fluxes vanish at the horizon and the spatial infinity. Finally, we discuss the role of the negative energy density near the horizon in the evaporating black hole.

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.

Sign in / Sign up

Export Citation Format

Share Document