780 research outputs found
Apparent Horizons with Nontrivial Topology and the Hyperhoop Conjecture in Six-Dimensional Space-Times
We investigate the validity of the hyperhoop conjecture, which claims to
determine a necessary and sufficient condition for the formation of black hole
horizons in higher-dimensional space-times. Here we consider momentarily
static, conformally flat initial data sets each describing a gravitational
field of uniform massive k-sphere sources, for k=1,2, on the five-dimensional
Cauchy surface. The numerical result shows the validity of the hyperhoop
conjecture for a wide range of model parameters. We also confirm for the first
time the existence of an apparent horizon homeomorphism to S**2 x S**2 or S**1
x S**3, which is a higher-dimensional generalization of the black ring.Comment: 17 pages, 12 figures. to appear in Phys. Rev.
Electromagnetic radiation due to naked singularity formation in self-similar gravitational collapse
Dynamical evolution of test fields in background geometry with a naked
singularity is an important problem relevant to the Cauchy horizon instability
and the observational signatures different from black hole formation. In this
paper we study electromagnetic perturbations generated by a given current
distribution in collapsing matter under a spherically symmetric self-similar
background. Using the Green's function method, we construct the formula to
evaluate the outgoing energy flux observed at the future null infinity. The
contributions from "quasi-normal" modes of the self-similar system as well as
"high-frequency" waves are clarified. We find a characteristic power-law time
evolution of the outgoing energy flux which appears just before naked
singularity formation, and give the criteria as to whether or not the outgoing
energy flux diverges at the future Cauchy horizon.Comment: 20 pages, 7 figures, references added to match the published versio
Black ring formation in particle systems
It is known that the formation of apparent horizons with non-spherical
topology is possible in higher-dimensional spacetimes. One of these is the
black ring horizon with topology where is the spacetime
dimension number. In this paper, we investigate the black ring horizon
formation in systems with -particles. We analyze two kinds of system: the
high-energy -particle system and the momentarily-static -black-hole
initial data. In the high-energy particle system, we prove that the black ring
horizon does not exist at the instant of collision for any . But there
remains a possibility that the black ring forms after the collision and this
result is not sufficient. Because calculating the metric of this system after
the collision is difficult, we consider the momentarily-static -black-hole
initial data that can be regarded as a simplified -particle model and
numerically solve the black ring horizon that surrounds all the particles. Our
results show that there is the minimum particle number that is necessary for
the black ring formation and this number depends on . Although many particle
number is required in five-dimensions, is sufficient for the black ring
formation in the cases. The black ring formation becomes easier for
larger . We provide a plausible physical interpretation of our results and
discuss the validity of Ida and Nakao's conjecture for the horizon formation in
higher-dimensions. Finally we briefly discuss the probable methods of producing
the black rings in accelerators.Comment: 26 pages, 7 figure
Improved analysis of black hole formation in high-energy particle collisions
We investigate formation of an apparent horizon (AH) in high-energy particle
collisions in four- and higher-dimensional general relativity, motivated by
TeV-scale gravity scenarios. The goal is to estimate the prefactor in the
geometric cross section formula for the black hole production. We numerically
construct AHs on the future light cone of the collision plane. Since this slice
lies to the future of the slice used previously by Eardley and Giddings
(gr-qc/0201034) and by one of us and Nambu (gr-qc/0209003), we are able to
improve the prefactor estimates. The black hole production cross section
increases by 40-70% in the higher-dimensional cases, indicating larger black
hole production rates in future-planned accelerators than previously estimated.
We also determine the mass and the angular momentum of the final black hole
state, as allowed by the area theorem.Comment: 28 pages, 14 figures, references and minor comments adde
Nonaxisymmetric instability of rapidly rotating black hole in five dimensions
We present results from numerical solution of Einstein's equation in five
dimensions describing evolution of rapidly rotating black holes. We show, for
the first time, that the rapidly rotating black holes in higher dimensions are
unstable against nonaxisymmetric deformation; for the five-dimensional case,
the critical value of spin parameter for onset of the instability is .Comment: 4 pages, 3 figures, accepted for publication in PRD(R
Black hole initial data in Gauss-Bonnet gravity: Momentarily static case
We study the method for generating the initial data of black hole systems in
Gauss-Bonnet (GB) gravity. The initial data are assumed to be momentarily
static and conformally flat. Although the equation for the conformal factor is
highly nonlinear, it is successfully solved by numerical relaxation for
one-black-hole and two-black-hole systems. The common apparent horizon is
studied in the two-black-hole initial data, and the result suggests that the
Penrose inequalities are satisfied in this system. This is the first step for
simulating black hole collisions in higher-curvature theories.Comment: 30 pages, 10 figures, submitted to PR
Detecting gravitational waves from inspiraling binaries with a network of detectors : coherent strategies by correlated detectors
We discuss the coherent search strategy to detect gravitational waves from
inspiraling compact binaries by a network of correlated laser interferometric
detectors. From the maximum likelihood ratio statistic, we obtain a coherent
statistic which is slightly different from and generally better than what we
obtained in our previous work. In the special case when the cross spectrum of
two detectors normalized by the power spectrum density is constant, the new
statistic agrees with the old one. The quantitative difference of the detection
probability for a given false alarm rate is also evaluated in a simple case.Comment: 4 pages, 1 Postscript figures, uses revtex4.st
Highly distorted apparent horizons and the hoop conjecture
By analyzing the apparent horizon (AH) formation in the collision of two
pp-waves with rectangular sources in four dimensions, we study to what extent
the AH can be distorted without violating the energy conditions. It is shown
that the highly distorted AH can form in this system although it cannot be
arbitrarily long. The hoop conjecture is examined for the formation of such
highly distorted AHs, and our result gives a strong support to the hoop
conjecture. We also point out the possible relation between the AH topology
theorem and the hoop conjecture.Comment: 10 pages, 5 figures, submitted to PRD(R
High-energy head-on collisions of particles and hoop conjecture
We investigate the apparent horizon formation for high-energy head-on
collisions of particles in multi-dimensional spacetime. The apparent horizons
formed before the instance of particle collision are obtained analytically.
Using these solutions, we discuss the feature of the apparent horizon formation
in the multi-dimensional spacetime from the viewpoint of the hoop conjecture.Comment: 4pages, 4figure
On Detection of Black Hole Quasi-Normal Ringdowns: Detection Efficiency and Waveform Parameter Determination in Matched Filtering
Gravitational radiation from a slightly distorted black hole with ringdown
waveform is well understood in general relativity. It provides a probe for
direct observation of black holes and determination of their physical
parameters, masses and angular momenta (Kerr parameters). For ringdown searches
using data of gravitational wave detectors, matched filtering technique is
useful. In this paper, we describe studies on problems in matched filtering
analysis in realistic gravitational wave searches using observational data.
Above all, we focus on template constructions, matches or signal-to-noise
ratios (SNRs), detection probabilities for Galactic events, and accuracies in
evaluation of waveform parameters or black hole hairs. We have performed
matched filtering analysis for artificial ringdown signals which are generated
with Monte-Carlo technique and injected into the TAMA300 observational data. It
is shown that with TAMA300 sensitivity, the detection probability for Galactic
ringdown events is about 50% for black holes of masses greater than with SNR . The accuracies in waveform parameter estimations
are found to be consistent with the template spacings, and resolutions for
black hole masses and the Kerr parameters are evaluated as a few % and , respectively. They can be improved up to and for events
of by using fine-meshed template bank in the hierarchical
search strategy.Comment: 10 pages, 10 figure
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