scholarly journals On the Counter-Rotation of Closed Time-like Curves

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 28
Author(s):  
Yuanyuan Duan ◽  
Fangxun Liu ◽  
Yu Wang ◽  
Yen Chin Ong
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Angular Velocity ◽  
Physical Interpretation ◽  
Short Note ◽  
Black Hole Horizon ◽  
Time Orientation ◽  
Physical Understanding ◽  
Counter Rotation ◽  
Rotating Bodies

While it is tempting to think of closed time-like curves (CTCs) around rotating bodies, such as a black hole, as being “caused” by the rotation of the source, Andréka et al. pointed out that the underlying physics are not as straightforward as this, since such CTCs are “counter-rotating”, i.e., the time orientation (the opening of the local light cones) of the CTCs is opposite to the direction in which the singularity or the ergosphere rotates. It was also suggested that this is a generic phenomenon that calls for a deeper intuitive physical understanding. In this short note, we point out—with Kerr–Taub–NUT as an example—that CTCs are counter-rotating with respect to the local angular velocity of the spacetime, not the global angular momentum, nor the angular velocity of the black hole horizon, which makes the physical interpretation of CTCs being “caused” by a rotating source even more problematic.

Why only a small fraction of quasars are radio loud?

2018 ◽  
Vol 14 (S342) ◽  
pp. 201-204
Author(s):  
Xinwu Cao
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Angular Momentum ◽  
Angular Velocity ◽  
Strong Magnetic Field ◽  
Weak Magnetic Field ◽  
Thin Disk ◽  
Relativistic Jets ◽  
Jet Formation ◽  
The Magnetic Field

AbstractIt is still a mystery why only a small fraction of quasars contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation. Gas falls from the Bondi radius RB nearly freely to the circularization radius Rc, and a thin accretion disk is formed within Rc We suggest that the external weak magnetic field threading interstellar medium is substantially enhanced in this region, and the magnetic field at Rc can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at RB. In this case, the magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. If the angular velocity of the circumnuclear gas is low, the field advection in the thin disk is inefficient, and it will appear as a radio-quiet (RQ) quasar.

From Schwarzschild to Kerr under de Sitter background due to blackhole tunnelling

2007 ◽  
Vol 85 (8) ◽  
pp. 863-868 ◽  
Author(s):  
K Xiao ◽  
W Liu
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Event Horizon ◽  
Hawking Radiation ◽  
Emission Rate ◽  
Momentum Conservation ◽  
Black Hole Horizon ◽  
De Sitter ◽  
Quantum Tunnelling ◽  
Sitter Background

When a particle with angular momentum tunnels across the event horizon of Schwarzschild–de Sitter black hole, the black hole will change into a Kerr–de Sitter one. Considering Hawking radiation as a process of quantum tunnelling near a black-hole horizon, the emission rate of the particles with angular momentum is calculated under energy and angular momentum conservation, and the result is consistent with an underlying unitary theory.PACS Nos.: 97.60.Lf, 04.70.Dy, 03.65.Pm

BLACK HOLES HAVE LONG HAIR

2012 ◽  
Vol 21 (11) ◽  
pp. 1242003 ◽  
Author(s):  
SHAHAR HOD
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Spatial Behavior ◽  
Black Hole Horizon ◽  
Hairy Black Holes ◽  
Matter Fields ◽  
Circular Geodesic ◽  
Hairy Black Hole

The influential "no-hair" conjecture suggests that black holes may be characterized by only three conserved parameters: mass, charge and angular momentum. However, counterexamples in which the conjecture fails are well-known in the literature. In this essay we study such Einstein-matter theories in which hairy black-hole configurations have been discovered. In particular, we analyze the spatial behavior of the matter fields which reside outside the black-hole horizon. We prove a theorem which reveals the central role played by the null circular geodesic (the "photonsphere") of such hairy black holes. According to this theorem, the asymptotic decline of the hair outside the horizon cannot start before the black-hole photonsphere is crossed. We therefore conclude that hairy black holes must have long hair which extends beyond the photonsphere.

scholarly journals ACCELERATION OF PARTICLES BY QUASIBLACK HOLES

2013 ◽  
Vol 22 (06) ◽  
pp. 1350028 ◽  
Author(s):  
O. B. ZASLAVSKII
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Electric Charge ◽  
Center Of Mass ◽  
Finite Energy ◽  
Fine Tuning ◽  
Black Hole Horizon ◽  
Acceleration Of Particles ◽  
Bsw Effect

If two particles collide near the black hole horizon, the energy in their center of mass (CM) frame can grow indefinitely (the so-called Bañados, Silk and West (BSW) effect). This requires fine-tuning the parameters (the energy–momentum, angular momentum or electric charge) of one particle. We show that the CM energy can be unbound also for collisions in the spacetime of quasiblack holes (QBHs) (the objects on the threshold of forming the horizon which do not collapse). It does not require special fine-tuning of parameters and occurs when any particle inside a QBH having a finite energy collides with the particle that entered a QBH from the outside region.

scholarly journals GEOMETRIC TRANSPORT ALONG CIRCULAR ORBITS IN STATIONARY AXISYMMETRIC SPACETIMES

2004 ◽  
Vol 13 (09) ◽  
pp. 1771-1803 ◽  
Author(s):  
DONATO BINI ◽  
CHRISTIAN CHERUBINI ◽  
GIANLUCA CRUCIANI ◽  
ROBERT T. JANTZEN
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Angular Velocity ◽  
Electromagnetic Fields ◽  
Equatorial Plane ◽  
Parallel Transport ◽  
Inner Product ◽  
Circular Orbits ◽  
Kerr Spacetime ◽  
Parameter Dependent

Parallel transport along circular orbits in orthogonally transitive stationary axisymmetric spacetimes is described explicitly relative to Lie transport in terms of the electric and magnetic parts of the induced connection. The influence of both the gravito-electromagnetic fields associated with the zero angular momentum observers and of the Frenet–Serret parameters of these orbits as a function of their angular velocity is seen on the behavior of parallel transport through its representation as a parameter-dependent Lorentz transformation between these two inner-product preserving transports which is generated by the induced connection. This extends the analysis of parallel transport in the equatorial plane of the Kerr spacetime to the entire spacetime outside the black hole horizon, and helps give an intuitive picture of how competing "central attraction forces" and centripetal accelerations contribute with gravitomagnetic effects to explain the behavior of the 4-acceleration of circular orbits in that spacetime.

scholarly journals Super-Penrose process due to collisions inside ergosphere

2017 ◽  
Vol 26 (02) ◽  
pp. 1750009
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Black Hole Horizon ◽  
Mass Frame ◽  
Penrose Process

If two particles collide inside the ergosphere, the energy in the center of mass frame can be made unbound provided at least one of particles has a large negative angular momentum [A. A. Grib and Yu. V. Pavlov, Europhys. Lett. 101 (2013) 20004]. We show that the same condition can give rise to unbounded Killing energy of debris at infinity, i.e. super-Penrose process. Proximity of the point of collision to the black hole horizon is not required.

Rotating bodies; the Kerr metric

2021 ◽  
pp. 260-273
Author(s):  
Andrew M. Steane
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Kerr Black Hole ◽  
Kerr Metric ◽  
Kerr Solution ◽  
Limit Surface ◽  
Generic Properties ◽  
Rotating Body ◽  
Particle Orbits ◽  
Rotating Bodies

Spacetime around a general rigidly rotating body is discussed, and the Kerr solution explored in detail. First we obtain generic properties of stationary, axisymmetric metrics. The stationary limit surface and ergoregion is defined. Then the Kerr metric is presented (without derivation) and discussed. Horizons and limit surfaces are obtained, and the overall structure of the Kerr black hole deduced. The mass and angular momentum is extracted. Equations for particle orbits are obtained, and their properties discussed.

scholarly journals Comments on information erasure in black hole

2014 ◽  
Vol 29 (38) ◽  
pp. 1450199
Author(s):  
Mishkat Al Alvi ◽  
Md. Abdul Matin ◽  
Moinul Hossain Rahat ◽  
Avik Roy ◽  
Mahbub Majumdar
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Mutual Information ◽  
Event Horizon ◽  
Physical Interpretation ◽  
Black Hole Horizon ◽  
Landauer’S Principle ◽  
Physical Laws ◽  
Information Erasure

We analyze the Kim, Lee and Lee model of information erasure by black holes and find contradictions with standard physical laws. We demonstrate that the erasure model leads to arbitrarily fast information erasure; the proposed physical interpretation of information freezing at the event horizon as observed by an asymptotic observer is problematic; and information erasure, whatever the process may be, near the black hole horizon leads to contradictions with quantum mechanics if Landauer's principle is assumed. The later part of the work demonstrates the significance of the "erasure entropy". We show that the erasure entropy is the mutual information between two subsystems.

scholarly journals Infrared effects in the late stages of black hole evaporation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Éanna É. Flanagan
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Planck Scale ◽  
Black Hole Mass ◽  
Order Unity ◽  
Intrinsic Angular Momentum ◽  
Hole Position ◽  
Late Stages ◽  
Shear Tensor

Abstract As a black hole evaporates, each outgoing Hawking quantum carries away some of the black holes asymptotic charges associated with the extended Bondi-Metzner-Sachs group. These include the Poincaré charges of energy, linear momentum, intrinsic angular momentum, and orbital angular momentum or center-of-mass charge, as well as extensions of these quantities associated with supertranslations and super-Lorentz transformations, namely supermomentum, superspin and super center-of-mass charges (also known as soft hair). Since each emitted quantum has fluctuations that are of order unity, fluctuations in the black hole’s charges grow over the course of the evaporation. We estimate the scale of these fluctuations using a simple model. The results are, in Planck units: (i) The black hole position has a uncertainty of $$ \sim {M}_i^2 $$ ∼ M i 2 at late times, where Mi is the initial mass (previously found by Page). (ii) The black hole mass M has an uncertainty of order the mass M itself at the epoch when M ∼ $$ {M}_i^{2/3} $$ M i 2 / 3 , well before the Planck scale is reached. Correspondingly, the time at which the evaporation ends has an uncertainty of order $$ \sim {M}_i^2 $$ ∼ M i 2 . (iii) The supermomentum and superspin charges are not independent but are determined from the Poincaré charges and the super center-of-mass charges. (iv) The supertranslation that characterizes the super center-of-mass charges has fluctuations at multipole orders l of order unity that are of order unity in Planck units. At large l, there is a power law spectrum of fluctuations that extends up to l ∼ $$ {M}_i^2/M $$ M i 2 / M , beyond which the fluctuations fall off exponentially, with corresponding total rms shear tensor fluctuations ∼ MiM−3/2.

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