652 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.
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
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
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
Close-limit analysis for head-on collision of two black holes in higher dimensions: Brill-Lindquist initial data
Motivated by the TeV-scale gravity scenarios, we study gravitational
radiation in the head-on collision of two black holes in higher dimensional
spacetimes using a close-limit approximation. We prepare time-symmetric initial
data sets for two black holes (the so-called Brill-Lindquist initial data) and
numerically evolve the spacetime in terms of a gauge invariant formulation for
the perturbation around the higher-dimensional Schwarzschild black holes. The
waveform and radiated energy of gravitational waves emitted in the head-on
collision are clarified. Also, the complex frequencies of fundamental
quasinormal modes of higher-dimensional Schwarzschild black holes, which have
not been accurately derived so far, are determined.Comment: 27 pages, 8 figures, published versio
Spectral analysis of aegelin isolated from maja leaves (Aegle marmelos Corr.)
Aegelin is an alkaloid which isolated from Maja (Aegle marmelos Corr.) leaves. The molecular structure of the compound contains a chiral carbon atom. In our earlier publications the existence and influence of a chiral carbon atom have not been discussed yet. The existing of the chiral carbon atom gave rise two pair of doublets at d 3.67 J=3.4 Hz and d 3.43 J=8.5 Hz in the proton nmr spectrum. The doublets are signal of two proton which attached on adjacent atom of the chiral carbon atom which is confirmed bythe two dimension nmr spectrum (HMQC). The two protons are magnetic unequivalent which cause their chemical shifts are different. The protons appear as two doublet with different J value because its couple to a proton attached at the chiral carbon atom and the spin-spin splitting is observed. The existence of the two pairs of the doublets at d 3.67 d,J=3.4 Hz and d 3.42 d,J=8.5 Hz because the isolated aegelin from E.marmelos leaves contains of its enantimeer.Key words: E. marmelos, aegelin, enantiomeer, spectroscop
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
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
Detecting gravitational waves from inspiraling binaries with a network of detectors : coherent versus coincident strategies
We compare two strategies of multi-detector detection of compact binary
inspiral signals, namely, the coincidence and the coherent. For simplicity we
consider here two identical detectors having the same power spectral density of
noise, that of initial LIGO, located in the same place and having the same
orientation. We consider the cases of independent noise as well as that of
correlated noise. The coincident strategy involves separately making two
candidate event lists, one for each detector, and from these choosing those
pairs of events from the two lists which lie within a suitable parameter
window, which then are called as coincidence detections. The coherent strategy
on the other hand involves combining the data phase coherently, so as to obtain
a single network statistic which is then compared with a single threshold. Here
we attempt to shed light on the question as to which strategy is better. We
compare the performances of the two methods by plotting the Receiver Operating
Characteristics (ROC) for the two strategies. Several of the results are
obtained analytically in order to gain insight. Further we perform numerical
simulations in order to determine certain parameters in the analytic formulae
and thus obtain the final complete results. We consider here several cases from
the relatively simple to the astrophysically more relevant in order to
establish our results. The bottom line is that the coherent strategy although
more computationally expensive in general than the coincidence strategy, is
superior to the coincidence strategy - considerably less false dismissal
probability for the same false alarm probability in the viable false alarm
regime.Comment: 18 pages, 10 figures, typo correcte
Template banks to search for compact binaries with spinning components in gravitational wave data
Gravitational waves from coalescing compact binaries are one of the most
promising sources for detectors such as LIGO, Virgo and GEO600. If the
components of the binary posess significant angular momentum (spin), as is
likely to be the case if one component is a black hole, spin-induced precession
of a binary's orbital plane causes modulation of the gravitational-wave
amplitude and phase. If the templates used in a matched-filter search do not
accurately model these effects then the sensitivity, and hence the detection
rate, will be reduced. We investigate the ability of several search pipelines
to detect gravitational waves from compact binaries with spin. We use the
post-Newtonian approximation to model the inspiral phase of the signal and
construct two new template banks using the phenomenological waveforms of
Buonanno, Chen and Vallisneri. We compare the performance of these template
banks to that of banks constructed using the stationary phase approximation to
the non-spinning post-Newtonian inspiral waveform currently used by LIGO and
Virgo in the search for compact binary coalescence. We find that, at the same
false alarm rate, a search pipeline using phenomenological templates is no more
effective than a pipeline which uses non-spinning templates. We recommend the
continued use of the non-spinning stationary phase template bank until the
false alarm rate associated with templates which include spin effects can be
substantially reduced.Comment: 11 pages, 3 figure
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