Superresonance effect and energy flow in acoustic black holes

2006 ◽  
Vol 84 (6-7) ◽  
pp. 501-506 ◽  
Author(s):  
R Kobes
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Energy Flow ◽  
Numerical Solutions ◽  
Kerr Black Hole ◽  
Scalar Fields ◽  
Acoustic Black Holes ◽  
Analogous Effect

We study numerically the superresonance effect of scalar fields incident on an acoustic black hole. We show that the superresonance effect is quite large compared with the analogous effect in a Kerr black hole. We also do an analysis of the energy flow from these numerical solutions to determine where the outward flow of energy originates.PACS Nos.: 11.10.–z, 04.70.–s

Sound absorption based on Micro-perforated panels and Acoustic Black Hole principle

2021 ◽  
Vol 263 (6) ◽  
pp. 548-555
Author(s):  
Xiaoqi Zhang ◽  
Li Cheng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Sound Absorption ◽  
Practical Application ◽  
Inner Radius ◽  
Simulation Results ◽  
Structural Configurations ◽  
Acoustic Black Holes ◽  
Sound Reduction ◽  
Bending Wave

Acoustic black holes (ABHs) have been so far investigated mainly for bending wave ma-nipulation in mechanical structures such as beams or plates. The investigations on ABHs for sound wave manipulation, referred to as Sonic black holes (SBHs) are scarce. Existing SBH structure for sound reduction in air is typically formed by putting a set of rings inside a duct wall with decreasing inner radius according to a power law. As such, the structure is very complex and difficult to be practically realized, which hampers the practical application of SBHs for sound reduction. This study explores the possibilities of achieving SBH effects using other types of structural configurations. In particular, micro-perforated panels are proposed to be introduced into the conventional SBH structure, and the simulation results show that the new formed SBH structure is simpler in configuration in terms of number of rings and more efficient in terms of sound energy trapping and dissipation.

scholarly journals Statistical Properties of Kerr BH Flywheel Model of QSOs/AGNs

2000 ◽  
Vol 195 ◽  
pp. 417-418
Author(s):  
S. Nitta
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Kerr Black Hole ◽  
Mass Function ◽  
Initial Mass Function ◽  
Number Density ◽  
Disk System ◽  
The Press ◽  
The Individual ◽  
Density Population

The aim of this work is to demonstrate the properties of the magnetospheric model around Kerr black holes, so-called the “flywheel” (rotation powered) model. The fly-wheel engine of the BH accretion disk system is applied to the statistics of QSOs/AGNs. Nitta, Takahashi, & Tomimatsu clarified the individual evolution of the Kerr black-hole fly-wheel engine, which is parameterized by black-hole mass, initial Kerr parameter, magnetic field near the horizon, and a dimensionless small parameter. We impose a statistical model for the initial mass function of an ensemble of black holes using the Press-Schechter formalism. With the help of additional assumptions, we can discuss the evolution of the luminosity function and the spatial number density (population) of QSOs/AGNs. The result explains well the decrease of very bright QSOs and decrease of population after z ~ 2.

Bound orbits around modified Hayward black holes

2021 ◽  
Author(s):  
Bo Gao ◽  
Xue-Mei Deng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Periodic Orbits ◽  
Kerr Black Hole ◽  
Periodic Oscillations ◽  
Test Particles ◽  
Spin Parameter ◽  
Bound Orbits

The neutral time-like particle’s bound orbits around modified Hayward black holes have been investigated. We find that both in the marginally bound orbits (MBO) and the innermost stable circular orbits (ISCO), the test particle’s radius and its angular momentum are all more sensitive to one of the parameters [Formula: see text]. Especially, modified Hayward black holes with [Formula: see text] could mimic the same ISCO radius around the Kerr black hole with the spin parameter up to [Formula: see text]. Small [Formula: see text] could mimic the ISCO of small-spinning test particles around Schwarzschild black holes. Meanwhile, rational (periodic) orbits around modified Hayward black holes have also been studied. The epicyclic frequencies of the quasi-circular motion around modified Hayward black holes are calculated and discussed with respect to the observed Quasi-periodic oscillations (QPOs) frequencies. Our results show that rational orbits around modified Hayward black holes have different values of the energy from the ones of Schwarzschild black holes. The epicyclic frequencies in modified Hayward black holes have different frequencies from Schwarzschild and Kerr ones. These might provide hints for distinguishing modified Hayward black holes from Schwarzschild and Kerr ones by using the dynamics of time-like particles around the strong gravitational field.

scholarly journals QUASINORMAL MODES AND LATE-TIME TAILS OF CANONICAL ACOUSTIC BLACK HOLES

2007 ◽  
Vol 16 (07) ◽  
pp. 1211-1218 ◽  
Author(s):  
PING XI ◽  
XIN-ZHOU LI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Wave Propagation ◽  
Angular Momentum ◽  
Numerical Method ◽  
Time Scale ◽  
Quasinormal Modes ◽  
Late Time ◽  
Classical Wave ◽  
Acoustic Black Holes

In this paper, we investigate the evolution of classical wave propagation in the canonical acoustic black hole by a numerical method and discuss the details of the tail phenomenon. The oscillating frequency and damping time scale both increase with the angular momentum l. For lower l, numerical results show the lowest WKB approximation gives the most reliable result. We also find that the time scale of the interim region from ringing to tail is not affected obviously by changing l.

scholarly journals ON BLACK HOLE CREATION IN PLANCKIAN ENERGY SCATTERING

1996 ◽  
Vol 05 (06) ◽  
pp. 707-721 ◽  
Author(s):  
I. YA. AREF’EVA ◽  
I.V. VOLOVICH ◽  
K.S. VISWANATHAN
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Waves ◽  
Black Hole Solution ◽  
Kerr Black Hole ◽  
Energy Scattering ◽  
Light Particles ◽  
Black Hole Creation ◽  
Plane Gravitational Waves

In a series of papers Amati, Ciafaloni and Veneziano and ’t Hooft conjectured that black holes occur in the collision of two light particles at planckian energies. In this talk based on [10] we discuss a possible scenario for such a process by using the Chandrasekhar-Ferrari-Xanthopoulos duality between the Kerr black hole solution and colliding plane gravitational waves.

scholarly journals Superresonance phenomenon from acoustic black holes in neo-Newtonian theory

2016 ◽  
Vol 25 (05) ◽  
pp. 1650055 ◽  
Author(s):  
I. G. Salako ◽  
Abdul Jawad
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Sound Wave ◽  
Black Hole Mass ◽  
Newtonian Theory ◽  
Acoustic Black Holes ◽  
Bathtub Model

We explore the possibility of the acoustic analogue of a super-radiance like phenomenon, i.e. the amplification of a sound wave by reflection from the ergo-region of a rotating acoustic black hole in the fluid draining bathtub model in the presence of the pressure to be amplified or reduced in agreement with the value of the parameter [Formula: see text]. We remark that the interval of frequencies depend upon the neo-Newtonian parameter [Formula: see text] ([Formula: see text]) and becomes narrow in this work. As a consequence, the tuning of the neo-Newtonian parameter [Formula: see text] changes the rate of loss of the acoustic black hole mass.

scholarly journals SEMICLASSICAL CORRECTIONS TO THE CARDY–VERLINDE FORMULA OF KERR BLACK HOLES

2008 ◽  
Vol 23 (13) ◽  
pp. 2047-2053 ◽  
Author(s):  
M. R. SETARE
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Central Charge ◽  
Kerr Black Hole ◽  
Gravitational Effect ◽  
The Self ◽  
Entropy Formula ◽  
Verlinde Formula ◽  
Kerr Black Holes

In this paper, we compute the corrections to the Cardy–Verlinde formula of four-dimensional Kerr black hole. These corrections are considered within the context of KKW analysis and arise as a result of the self-gravitational effect. Then we show that one can take into account the semiclassical corrections of the Cardy–Verlinde entropy formula by only redefining the Virasoro operator L0 and the central charge c.

scholarly journals Global embeddings and hydrodynamic properties of Kerr black hole

2016 ◽  
Vol 31 (35) ◽  
pp. 1650204
Author(s):  
Soon-Tae Hong
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equatorial Plane ◽  
Kerr Black Hole ◽  
Kerr Spacetime ◽  
Stable Circular Orbit ◽  
Massive Particles ◽  
Flat Embedding ◽  
Bound Orbits ◽  
The Impact

In the presence of a rotating Kerr black hole, we investigate hydrodynamics of the massive particles and massless photons to construct relations among number density, pressure and internal energy density of the massive particles and photons around the rotating Kerr black hole and to study an accretion onto the black hole. On equatorial plane of the Kerr black hole, we investigate the bound orbits of the massive particles and photons around the black hole to produce their radial, azimuthal and precession frequencies. With these frequencies, we study the black holes GRO J1655-40 and 4U 1543-47 to explicitly obtain the radial, azimuthal and precession frequencies of the massive particles in the flow of perfect fluid. We next consider the massive particles in the stable circular orbit of radius of 1.0 ly around the supernovas SN 1979C, SN 1987A and SN 2213-1745 in the Kerr curved spacetime, and around the potential supermassive Schwarzschild black holes M87, NGC 3115, NGC 4594, NGC 3377, NGC 4258, M31, M32 and Galatic center, to estimate their radial and azimuthal frequencies, which are shown to be the same results as those in no precession motion. The photon unstable orbit is also discussed in terms of the impact parameter of the photon trajectory. Finally, on the equatorial plane of the Kerr black hole, we construct the global flat embedding structures possessing (9 + 3) dimensionalities outside and inside the event horizon of the rotating Kerr black hole. Moreover, on the plane, we investigate the warp products of the Kerr spacetime.

scholarly journals AREA SPECTRUM OF KERR AND EXTREMAL KERR BLACK HOLES FROM QUASINORMAL MODES

2005 ◽  
Vol 20 (25) ◽  
pp. 1923-1932 ◽  
Author(s):  
MOHAMMAD R. SETARE ◽  
ELIAS C. VAGENAS
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Quasinormal Modes ◽  
Kerr Black Hole ◽  
Area Spectrum ◽  
The Real ◽  
Hole Area ◽  
Newman Black Hole ◽  
Discrete Area ◽  
Kerr Black Holes

Motivated by the recent interest in quantization of black hole area spectrum, we consider the area spectrum of Kerr and extremal Kerr black holes. Based on the proposal by Bekenstein and others that the black hole area spectrum is discrete and equally spaced, we implement Kunstatter's method to derive the area spectrum for the Kerr and extremal Kerr black holes. The real part of the quasinormal frequencies of Kerr black hole used for this computation is of the form mΩ where Ω is the angular velocity of the black hole horizon. The resulting spectrum is discrete but not as expected uniformly spaced. Thus, we infer that the function describing the real part of quasinormal frequencies of Kerr black hole is not the correct one. This conclusion is in agreement with the numerical results for the highly damped quasinormal modes of Kerr black hole recently presented by Berti, Cardoso and Yoshida. On the contrary, extremal Kerr black hole is shown to have a discrete area spectrum which in addition is evenly spaced. The area spacing derived in our analysis for the extremal Kerr black hole area spectrum is not proportional to ln 3. Therefore, it does not give support to Hod's statement that the area spectrum [Formula: see text] should be valid for a generic Kerr–Newman black hole.

Stationary bound states of massless scalar fields around black holes and black hole analogues

2015 ◽  
Vol 24 (09) ◽  
pp. 1542018 ◽  
Author(s):  
Carolina L. Benone ◽  
Luís C. B. Crispino ◽  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Distribution ◽  
Scalar Field ◽  
Bound States ◽  
Neumann Boundary ◽  
Mass Term ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Field System

We discuss stationary bound states, a.k.a. clouds, for a massless test scalar field around Kerr black holes (BHs) and spinning acoustic BH analogues. In view of the absence of a mass term, the trapping is achieved via enclosing the BH — scalar field system in a cavity and imposing Dirichlet or Neumann boundary conditions. We discuss the variation of these bounds states with the discrete parameters that label them, as well as their spatial distribution, complementing results in our previous work [C. L. Benone, L. C. B. Crispino, C. Herdeiro and E. Radu, Phys. Rev. D91 (2015) 104038].

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