scholarly journals Magnetosphere structure of a Kerr black hole: Marginally force-free equatorial boundary condition

2018 ◽  
Vol 98 (4) ◽  
Author(s):  
Zhen Pan
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Kerr Black Hole

scholarly journals Gravitational wave echoes induced by a point mass plunging into a black hole

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Norichika Sago ◽  
Takahiro Tanaka
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Gravitational Wave ◽  
Previous Analysis ◽  
Kerr Black Hole ◽  
Frequency Component ◽  
Point Mass ◽  
Linear Perturbation ◽  
Perturbation Equation ◽  
Incident Waves

Abstract Recently, the possibility of detecting gravitational wave echoes in the data stream subsequent to the binary black hole mergers observed by LIGO was suggested. Motivated by this suggestion, we presented templates of echoes based on black hole perturbations in our previous work. There, we assumed that the incident waves resulting in echoes are similar to the ones that directly escape to the asymptotic infinity. In this work, to extract more reliable information on the waveform of echoes without using the naive assumption on the incident waves, we investigate gravitational waves induced by a point mass plunging into a Kerr black hole. We solve the linear perturbation equation with the source term induced by the plunging mass under the purely outgoing boundary condition at infinity and a hypothetical reflection boundary condition near the horizon. We find that the low-frequency component below the threshold of the super-radiant instability is highly suppressed, which is consistent with the incident waveform assumed in the previous analysis. We also find that the high-frequency mode excitation is significantly larger than the one used in the previous analysis, if we adopt the perfectly reflective boundary condition independently of the frequency. When we use a simple template in which the same waveform as the direct emissions to infinity is repeated with the decreasing amplitude, the correlation between the expected signal and the template turns out to decrease very rapidly.

scholarly journals Choked accretion onto a Kerr black hole

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Alejandro Aguayo-Ortiz ◽  
Olivier Sarbach ◽  
Emilio Tejeda
Keyword(s):  
Black Hole ◽  
Kerr Black Hole

scholarly journals Influence of the geometric configuration of accretion flow on the black hole spin dependence of relativistic acoustic geometry

2018 ◽  
Vol 27 (03) ◽  
pp. 1850023 ◽  
Author(s):  
Pratik Tarafdar ◽  
Tapas K. Das
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Geometric Configuration ◽  
Surface Gravity ◽  
Linear Perturbation ◽  
Flow Profile ◽  
White Hole ◽  
Accretion Flow ◽  
Black Hole Spin ◽  
General Relativistic

Linear perturbation of general relativistic accretion of low angular momentum hydrodynamic fluid onto a Kerr black hole leads to the formation of curved acoustic geometry embedded within the background flow. Characteristic features of such sonic geometry depend on the black hole spin. Such dependence can be probed by studying the correlation of the acoustic surface gravity [Formula: see text] with the Kerr parameter [Formula: see text]. The [Formula: see text]–[Formula: see text] relationship further gets influenced by the geometric configuration of the accretion flow structure. In this work, such influence has been studied for multitransonic shocked accretion where linear perturbation of general relativistic flow profile leads to the formation of two analogue black hole-type horizons formed at the sonic points and one analogue white hole-type horizon which is formed at the shock location producing divergent acoustic surface gravity. Dependence of the [Formula: see text]–[Formula: see text] relationship on the geometric configuration has also been studied for monotransonic accretion, over the entire span of the Kerr parameter including retrograde flow. For accreting astrophysical black holes, the present work thus investigates how the salient features of the embedded relativistic sonic geometry may be determined not only by the background spacetime, but also by the flow configuration of the embedding matter.

Entropy Correction for Kerr Black Hole

2005 ◽  
Vol 44 (6) ◽  
pp. 1037-1040
Author(s):  
Ren Zhao ◽  
Sheng-Li Zhang
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Entropy Correction

scholarly journals Extreme black hole anabasis

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Shahar Hadar ◽  
Alexandru Lupsasca ◽  
Achilleas P. Porfyriadis
Keyword(s):  
Boundary Condition ◽  
Black Hole ◽  
Spherically Symmetric ◽  
Asymptotically Flat ◽  
Flat Region ◽  
Extreme Black Hole ◽  
Condition Change ◽  
Birkhoff's Theorem ◽  
Birkhoff’S Theorem

Abstract We study the SL(2) transformation properties of spherically symmetric perturbations of the Bertotti-Robinson universe and identify an invariant μ that characterizes the backreaction of these linear solutions. The only backreaction allowed by Birkhoff’s theorem is one that destroys the AdS2× S2 boundary and builds the exterior of an asymptotically flat Reissner-Nordström black hole with $$ Q=M\sqrt{1-\mu /4} $$ Q = M 1 − μ / 4 . We call such backreaction with boundary condition change an anabasis. We show that the addition of linear anabasis perturbations to Bertotti-Robinson may be thought of as a boundary condition that defines a connected AdS2×S2. The connected AdS2 is a nearly-AdS2 with its SL(2) broken appropriately for it to maintain connection to the asymptotically flat region of Reissner-Nordström. We perform a backreaction calculation with matter in the connected AdS2× S2 and show that it correctly captures the dynamics of the asymptotically flat black hole.

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