963 research outputs found

### Bayesian model selection for testing the no-hair theorem with black hole ringdowns

General relativity predicts that a black hole that results from the merger of
two compact stars (either black holes or neutron stars) is initially highly
deformed but soon settles down to a quiescent state by emitting a superposition
of quasi-normal modes (QNMs). The QNMs are damped sinusoids with characteristic
frequencies and decay times that depend only on the mass and spin of the black
hole and no other parameter - a statement of the no-hair theorem. In this paper
we have examined the extent to which QNMs could be used to test the no-hair
theorem with future ground- and space-based gravitational-wave detectors. We
model departures from general relativity (GR) by introducing extra parameters
which change the mode frequencies or decay times from their general
relativistic values. With the aid of numerical simulations and Bayesian model
selection, we assess the extent to which the presence of such a parameter could
be inferred, and its value estimated. We find that it is harder to decipher the
departure of decay times from their GR value than it is with the mode
frequencies. Einstein Telescope (ET, a third generation ground-based detector)
could detect departures of <1% in the frequency of the dominant QNM mode of a
500 Msun black hole, out to a maximum range of 4 Gpc. In contrast, the New
Gravitational Observatory (NGO, an ESA space mission to detect gravitational
waves) can detect departures of ~ 0.1% in a 10^8 Msun black hole to a
luminosity distance of 30 Gpc (z = 3.5).Comment: 9 pages, 5 figure

### The Missing Link: Bayesian Detection and Measurement of Intermediate-Mass Black-Hole Binaries

We perform Bayesian analysis of gravitational-wave signals from non-spinning,
intermediate-mass black-hole binaries (IMBHBs) with observed total mass,
$M_{\mathrm{obs}}$, from $50\mathrm{M}_{\odot}$ to $500\mathrm{M}_{\odot}$ and
mass ratio 1\mbox{--}4 using advanced LIGO and Virgo detectors. We employ
inspiral-merger-ringdown waveform models based on the effective-one-body
formalism and include subleading modes of radiation beyond the leading $(2,2)$
mode. The presence of subleading modes increases signal power for inclined
binaries and allows for improved accuracy and precision in measurements of the
masses as well as breaking of extrinsic parameter degeneracies. For low total
masses, $M_{\mathrm{obs}} \lesssim 50 \mathrm{M}_{\odot}$, the observed chirp
mass $\mathcal{M}_{\rm obs} = M_{\mathrm{obs}}\,\eta^{3/5}$ ($\eta$ being the
symmetric mass ratio) is better measured. In contrast, as increasing power
comes from merger and ringdown, we find that the total mass $M_{\mathrm{obs}}$
has better relative precision than $\mathcal{M}_{\rm obs}$. Indeed, at high
$M_{\mathrm{obs}}$ ($\geq 300 \mathrm{M}_{\odot}$), the signal resembles a
burst and the measurement thus extracts the dominant frequency of the signal
that depends on $M_{\mathrm{obs}}$. Depending on the binary's inclination, at
signal-to-noise ratio (SNR) of $12$, uncertainties in $M_{\mathrm{obs}}$ can be
as large as \sim 20 \mbox{--}25\% while uncertainties in $\mathcal{M}_{\rm
obs}$ are \sim 50 \mbox{--}60\% in binaries with unequal masses (those
numbers become $\sim 17\%$ versus $\sim22\%$ in more symmetric binaries).
Although large, those uncertainties will establish the existence of IMBHs. Our
results show that gravitational-wave observations can offer a unique tool to
observe and understand the formation, evolution and demographics of IMBHs,
which are difficult to observe in the electromagnetic window. (abridged)Comment: 17 pages, 9 figures, 2 tables; updated to reflect published versio

### Is black-hole ringdown a memory of its progenitor?

We have performed an extensive numerical study of coalescing black-hole
binaries to understand the gravitational-wave spectrum of quasi-normal modes
excited in the merged black hole. Remarkably, we find that the masses and spins
of the progenitor are clearly encoded in the mode spectrum of the ringdown
signal. Some of the mode amplitudes carry the signature of the binary's mass
ratio, while others depend critically on the spins. Simulations of precessing
binaries suggest that our results carry over to generic systems. Using Bayesian
inference, we demonstrate that it is possible to accurately measure the mass
ratio and a proper combination of spins even when the binary is itself
invisible to a detector. Using a mapping of the binary masses and spins to the
final black hole spin, allows us to further extract the spin components of the
progenitor. Our results could have tremendous implications for gravitational
astronomy by facilitating novel tests of general relativity using merging black
holes.Comment: 5 pages, 3 figures, 1 table, accepted for publication in Physical
Review Letter

### Searching for binary coalescences with inspiral templates: Detection and parameter estimation

There has been remarkable progress in numerical relativity recently. This has
led to the generation of gravitational waveform signals covering what has been
traditionally termed the three phases of the coalescence of a compact binary -
the inspiral, merger and ringdown. In this paper, we examine the usefulness of
inspiral only templates for both detection and parameter estimation of the full
coalescence waveforms generated by numerical relativity simulations. To this
end, we deploy as search templates waveforms based on the effective one-body
waveforms terminated at the light-ring as well as standard post-Newtonian
waveforms. We find that both of these are good for detection of signals.
Parameter estimation is good at low masses, but degrades as the mass of the
binary system increases.Comment: 14 pages, submitted to proceedings of the NRDA08 meeting, Syracuse,
Aug. 11-14, 200

### Improved filters for gravitational waves from inspiraling compact binaries

The order of the post-Newtonian expansion needed to extract in a reliable and accurate manner the fully general relativistic gravitational wave signal from inspiraling compact binaries is explored. A class of approximate wave forms, called P-approximants, is constructed based on the following two inputs: (a) the introduction of two new energy-type and flux-type functions e(v) and f(v), respectively, (b) the systematic use of the PadÃ© approximation for constructing successive approximants of e(v) and f(v). The new P-approximants are not only more effectual (larger overlaps) and more faithful (smaller biases) than the standard Taylor approximants, but also converge faster and monotonically. The presently available (v/c)^5-accurate post-Newtonian results can be used to construct P-approximate wave forms that provide overlaps with the exact wave form larger than 96.5%, implying that more than 90% of potential events can be detected with the aid of P-approximants as opposed to a mere 10â€“15 % that would be detectable using standard post-Newtonian approximants

### The Evolution of Voids in the Adhesion Approximation

We apply the adhesion approximation to study the formation and evolution of
voids in the Universe. Our simulations -- carried out using 128$^3$ particles
in a cubical box with side 128 Mpc -- indicate that the void spectrum evolves
with time and that the mean void size in the standard COBE-normalised Cold Dark
Matter (hereafter CDM) model with $h_{50} = 1,$ scales approximately as $\bar
D(z) = {\bar D_0\over \sqrt {1+z}},$ where $\bar D_0 \simeq 10.5$ Mpc.
Interestingly, we find a strong correlation between the sizes of voids and the
value of the primordial gravitational potential at void centers. This
observation could in principle, pave the way towards reconstructing the form of
the primordial potential from a knowledge of the observed void spectrum.
Studying the void spectrum at different cosmological epochs, for spectra with a
built in $k$-space cutoff we find that, the number of voids in a representative
volume evolves with time. The mean number of voids first increases until a
maximum value is reached (indicating that the formation of cellular structure
is complete), and then begins to decrease as clumps and filaments merge leading
to hierarchical clustering and the subsequent elimination of small voids. The
cosmological epoch characterizing the completion of cellular structure occurs
when the length scale going nonlinear approaches the mean distance between
peaks of the gravitational potential. A central result of this paper is thatComment: Plain TeX, 38 pages Plus 16 Figures (available on request from the
first author), IUCAA-28 To appear in The Astrophysical Journal, July 199

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