1,159 research outputs found
Black-Hole Perturbation Plus Post-Newtonian Theory: Hybrid Waveform for Neutron Star Binaries
We consider the motion of nonspinning, compact objects orbiting around a Kerr
black hole with tidal couplings. The tide-induced quadrupole moment modifies
both the orbital energy and outgoing fluxes, so that over the inspiral
timescale there is an accumulative shift in the orbital and gravitational wave
phase. Previous studies on compact object tidal effects have been carried out
in the Post-Newtonian (PN) and Effective-One-Body (EOB) formalisms. In this
work, within the black hole perturbation framework, we propose to characterize
the tidal influence in the expansion of mass ratios, while higher-order PN
corrections are naturally included. For the equatorial and circular orbit, we
derive the leading order, frequency dependent tidal phase shift which agrees
with the Post-Newtonian result at low frequencies but deviates at high
frequencies. We also find that such phase shift has weak dependence () on the spin of the primary black hole. Combining this black hole
perturbation waveform with the Post-Newtonian waveform, we propose a
frequency-domain, hybrid waveform that shows comparable accuracy as the EOB
waveform in characterizing the tidal effects, as calibrated by numerical
relativity simulations. Further improvement is expected as the next-leading
order in mass ratio and the higher-PN tidal corrections are included. This
hybrid approach is also applicable for generating binary black hole waveforms.Comment: 20 pages, 5 figure
An Analytic Solution of Hydrodynamic Equations with Source Terms in Heavy Ion Collisions
The energy and baryon densities in heavy ion collisions are estimated by
analytically solving a 1+1 dimensional hydrodynamical model with source terms.
Particularly, a competition between the energy and baryon sources and the
expansion of the system is discussed in detail.Comment: LaTeX2e, 7 pages, 4 postscript figures, submitted to Int. J. Mod.
Phys.
Efficient fully precessing gravitational waveforms for binaries with neutron stars
We construct an efficient frequency domain waveform for generic circular
compact object binaries that include neutron stars. The orbital precession is
solved on the radiation reaction timescale (and then transformed to the
frequency domain), which is used to map the non-precessional waveform from the
source frame of the binary to the lab frame. The treatment of orbital
precession is different from that for precessional binary black holes, as
is no longer conserved due to the spin-induced quadrupole
moments of neutron stars. We show that the new waveform achieves
mismatch compared with waveforms generated by numerically evolved precession
for neutron star-black hole systems for configurations with
component mass/spin magnitude assumed in the analysis and randomized initial
spin directions. We expect this waveform to be useful to test the nature of the
mass-gap objects similar to the one discovered in GW 190814 by measuring their
spin-induced quadrupole moments, as it is possible that these mass-gap objects
are rapidly spinning. It is also applicable for the tests of black hole
mimickers in precessional binary black hole events, if the black hole mimicker
candidates have nontrivial spin-induced quadrupole moments.Comment: Corrected minor typos and a typo in Fig 9 resulting in the incorrect
placement in the image
Probing Spin-Induced Quadrupole Moments in Precessing Compact Binaries
Spin-induced quadrupole moments provide an important characterization of
compact objects, such as black holes, neutron stars and black hole mimickers
inspired by additional fields and/or modified theories of gravity. Black holes
in general relativity have a specific spin-induced quadrupole moment, with
other objects potentially having differing values. Different values of this
quadrupole moment lead to modifications of the spin precession dynamics, and
consequently modifications to the inspiral waveform. Based on the spin-dynamics
and the associated precessing waveform developed in our previous work, we
assess the prospects of measuring spin-induced moments in various black hole,
neutron star, and black-hole mimicker binaries. We focus on binaries in which
at least one of the objects is in the mass-gap (similar to the
object found in GW190814). We find that for generic precessing binaries, the
effect of the spin-induced quadrupole moments on the precession is sensitive to
the nature of the mass-gap object, i.e., whether it is a light black hole or a
massive neutron star. So that this is a good probe of the nature of these
objects. For precessing black-hole mimicker binaries, this waveform also
provides significantly tighter constraints on their spin-induced quadrupole
moments than the previous results obtained without incorporating the precession
effects of spin-induced quadrupole moments. We apply the waveform to sample
events in GWTC catalogs to obtain better constraints on the spin-induced
quadrupole moments, and discuss the measurement prospects for events in the
O run of the LIGO-Virgo-KAGRA collaboration.Comment: 14 pages, 10 figure
Deconfinement Phase Transition in an Expanding Quark system in Relaxation Time Approximation
We investigated the effects of nonequilibrium and collision terms on the
deconfinement phase transition of an expanding quark system in Friedberg-Lee
model in relaxation time approximation. By calculating the effective quark
potential, the critical temperature of the phase transition is dominated by the
mean field, while the collisions among quarks and mesons change the time
structure of the phase transition significantly.Comment: 7 pages, 7 figure
A scheme to fix multiple solutions in amplitude analyses
Decays of unstable heavy particles usually involve the coherent sum of
several amplitudes, like in a multiple slit experiment. Dedicated amplitude
analysis techniques have been widely used to resolve these amplitudes for
better understanding of the underlying dynamics. For special cases, where two
spin-1/2 particles and two (pseudo-)scalar particles are present in the
process, multiple equivalent solutions are found due to intrinsic symmetries in
the summed probability density function. In this paper, the problem of multiple
solutions is discussed and a scheme to overcome this problem is proposed by
fixing some free parameters. Toys are generated to validate the strategy. A new
approach to align helicities of initial- and final-state particles in different
decay chains is also introduced.Comment: 17 pages, 2 figure
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