2,482 research outputs found
How close can we approach the event horizon of the Kerr black hole from the detection of the gravitational quasinormal modes?
Using the WKB method, we show that the peak location () of the
potential, which determines the quasinormal mode frequency of the Kerr black
hole, obeys an accurate empirical relation as a function of the specific
angular momentum and the gravitational mass . If the quasinormal mode
with is observed by gravitational wave detectors, we can confirm
the black-hole space-time around the event horizon, where is the event horizon radius. While if the
quasinormal mode is different from that of general relativity, we are forced to
seek the true theory of gravity and/or face to the existence of the naked
singularity.Comment: 8 pages, 4 figure
Possible confirmation of the existence of ergoregion by the Kerr quasinormal mode in gravitational waves from Pop III massive black hole binary
The existence of the ergoregion of the Kerr space-time has not been confirmed
observationally yet. We show that the confirmation would be possible by
observing the quasinormal mode in gravitational waves. As an example, using the
recent population synthesis results of Pop III binary black holes, we find that
the peak of the final merger mass () is about , while
the fraction of the final spin needed for the
confirmation of a part of ergoregion is . To confirm the frequency
of the quasinormal mode, is needed. The standard model of Pop
III population synthesis tells us that the event rate for the confirmation of
more than of the ergoregion by the second generation gravitational wave
detectors is where and
are the peak value of the Pop III star formation rate and the
fraction of binaries, respectively.Comment: Accepted for publication in PTEP. Comments welcom
Gravitational wave quasinormal mode from Population III massive black hole binaries in various models of population synthesis
Focusing on the remnant black holes after merging binary black holes, we show
that ringdown gravitational waves of Population III binary black holes mergers
can be detected with the rate of
for various parameters and functions. This rate is estimated for the events
with SNR for the second generation gravitational wave detectors such as
KAGRA. Here, and are the peak value of the Population
III star formation rate and the fraction of binaries, respectively. When we
consider only the events with SNR, the event rate becomes . This suggest that for remnant black hole's spin
we have the event rate with SNR less than , while it is for the third generation detectors such as Einstein
Telescope. If we detect many Population III binary black holes merger, it may
be possible to constrain the Population III binary evolution paths not only by
the mass distribution but also by the spin distribution.Comment: Submitted to PTEP. comments welcom
Quarkyonic matter in lattice QCD at strong coupling
We study the phase diagram of quark matter at finite temperature and density
in the strong coupling lattice QCD with one species of unrooted staggered
fermions including finite coupling () effects for color SU(). We
find that we may have partially chiral restored medium density matter at
, which would correspond to the quarkyonic matter suggested at large
.Comment: 9 pages, 4 figure
Chiral and deconfinement transitions in strong coupling lattice QCD with finite coupling and Polyakov loop effects
We investigate chiral and deconfinement transitions in the framework of the
strong coupling lattice QCD for color SU(3) with one species of unrooted
staggered fermion at finite temperature and quark chemical potential. We take
account of the leading order Polyakov loop terms as well as the
next-to-next-to-leading order (1/g^4) fermionic terms of the strong coupling
expansion in the effective action. We investigate the Polyakov loop effects by
comparing two approximation schemes, a Haar measure method (no fluctuation from
the mean field) and a Weiss mean-field method (with fluctuations). The
effective potential is obtained in both cases, and we analytically clarify the
Polyakov loop contributions to the effective potential. The Polyakov loop is
found to suppress the chiral condensate and to reduce the chiral transition
temperature at mu=0, and the chiral transition temperature roughly reproduces
the Monte Carlo results at beta=2N_c/g^2 \lesssim 4. The deconfinement
transition is found to be the crossover and first order for light (am_0
\lesssim 4 at beta=4) and heavy quark masses, respectively.Comment: 13 pages, 15 figures. v2; More dicussions added, figures improved,
and typos correcte
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