scholarly journals Bound on the Lyapunov exponent in Kerr-Newman black holes via a charged particle

2022 ◽  
Vol 105 (2) ◽  
Author(s):  
Naoto Kan ◽  
Bogeun Gwak
Keyword(s):  
Black Holes ◽  
Charged Particle ◽  
Lyapunov Exponent

scholarly journals General stationary charged black holes as charged particle accelerators

2011 ◽  
Vol 84 (4) ◽  
Author(s):  
Yi Zhu ◽  
Shao-Feng Wu ◽  
Yu-Xiao Liu ◽  
Ying Jiang
Keyword(s):  
Black Holes ◽  
Charged Particle ◽  
Particle Accelerators ◽  
Charged Black Holes

OF CHARGED STARS AND CHARGED BLACK HOLES

2004 ◽  
Vol 13 (07) ◽  
pp. 1375-1379 ◽  
Author(s):  
MANUEL MALHEIRO ◽  
RODRIGO PICANÇO ◽  
SUBHARTHI RAY ◽  
JOSÉ P. S. LEMOS ◽  
VILSON T. ZANCHIN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Charged Particle ◽  
Equation Of State ◽  
Mass Density ◽  
Compact Star ◽  
Maximum Amount ◽  
Stellar Structure ◽  
Charged Black Holes ◽  
Polytropic Equation

Effect of maximum amount of charge a compact star can hold, is studied here. We analyze the different features in the renewed stellar structure and discuss the reasons why such huge charge is possible inside a compact star. We studied a particular case of a polytropic equation of state (EOS) assuming the charge density is proportional to the mass density. Although the global balance of force allows a huge charge, the electric repulsion faced by each charged particle forces it to leave the star, resulting in the secondary collapse of the system to form a charged black hole.

scholarly journals Lyapunov exponent, ISCO and Kolmogorov–Senai entropy for Kerr–Kiselev black hole

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Monimala Mondal ◽  
Farook Rahaman ◽  
Ksh. Newton Singh
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Lyapunov Exponent ◽  
Circular Orbit ◽  
Real Root ◽  
Angular Frequency ◽  
Geodesic Motion ◽  
Radial Equation ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

AbstractGeodesic motion has significant characteristics of space-time. We calculate the principle Lyapunov exponent (LE), which is the inverse of the instability timescale associated with this geodesics and Kolmogorov–Senai (KS) entropy for our rotating Kerr–Kiselev (KK) black hole. We have investigate the existence of stable/unstable equatorial circular orbits via LE and KS entropy for time-like and null circular geodesics. We have shown that both LE and KS entropy can be written in terms of the radial equation of innermost stable circular orbit (ISCO) for time-like circular orbit. Also, we computed the equation marginally bound circular orbit, which gives the radius (smallest real root) of marginally bound circular orbit (MBCO). We found that the null circular geodesics has larger angular frequency than time-like circular geodesics ($$Q_o > Q_{\sigma }$$ Q o > Q σ ). Thus, null-circular geodesics provides the fastest way to circulate KK black holes. Further, it is also to be noted that null circular geodesics has shortest orbital period $$(T_{photon}< T_{ISCO})$$ ( T photon < T ISCO ) among the all possible circular geodesics. Even null circular geodesics traverses fastest than any stable time-like circular geodesics other than the ISCO.

scholarly journals Null geodesics and QNMs in the field of regular black holes

2021 ◽  
pp. 2150095
Author(s):  
Monimala Mondal ◽  
Anil Kumar Yadav ◽  
Parthapratim Pradhan ◽  
Sayeedul Islam ◽  
Farook Rahaman
Keyword(s):  
Black Holes ◽  
Lyapunov Exponent ◽  
Circular Orbit ◽  
Eikonal Approximation ◽  
Angular Frequency ◽  
Massless Scalar ◽  
Null Geodesics ◽  
Regular Black Holes ◽  
Stable Circular Orbit ◽  
Scalar Perturbations

In this paper, we analyze the null geodesics of regular black holes (BHs). A detailed analysis of geodesic structure, both null geodesics and timelike geodesics, has been investigated for the said BH. As an application of null geodesics, we calculate the radius of photon sphere and gravitational bending of light. We also study the shadow of the BH spacetime. Moreover, we determine the relation between radius of photon sphere [Formula: see text] and the shadow observed by a distance observer. Furthermore, we discuss the effect of various parameters on the radius of shadow [Formula: see text]. Also, we compute the angle of deflection for the photons as a physical application of null-circular geodesics. We find the relation between null geodesics and quasinormal mode (QNM) frequency in the eikonal approximation by computing the Lyapunov exponent. It is also shown that (in the eikonal limit) the QNMs of BHs are governed by the parameter of null-circular geodesics. The real part of QNMs frequency determines the angular frequency, whereas the imaginary part determines the instability timescale of the circular orbit. Next, we study the massless scalar perturbations and analyze the effective potential graphically. Massive scalar perturbations are also discussed. As an application of timelike geodesics, we compute the innermost stable circular orbit (ISCO) and marginally bound circular orbit (MBCO) of the regular BHs which are closely related to the BH accretion disk theory. In the appendix, we calculate the relation between angular frequency and Lyapunov exponent for null-circular geodesics.

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