54,436 research outputs found
Gravitational-wave observations of binary black holes: Effect of non-quadrupole modes
We study the effect of non-quadrupolar modes in the detection and parameter
estimation of gravitational waves (GWs) from non-spinning black-hole binaries.
We evaluate the loss of signal-to-noise ratio and the systematic errors in the
estimated parameters when one uses a quadrupole-mode template family to detect
GW signals with all the relevant modes, for target signals with total masses
and mass ratios . Target
signals are constructed by matching numerical-relativity simulations describing
the late inspiral, merger and ringdown of the binary with
post-Newtonian/effective-one-body waveforms describing the early inspiral. We
find that waveform templates modeling only the quadrupolar modes of the GW
signal are sufficient (loss of detection rate ) for the detection of
GWs with mass ratios using advanced GW observatories. Neglecting the
effect of non-quadrupole modes will introduce systematic errors in the
estimated parameters. The systematic errors are larger than the expected
statistical errors for binaries with large, unequal masses
(), for sky-averaged signal-to-noise ratios
larger than . We provide a summary of the regions in the parameter space
where neglecting non-quadrupole modes will cause unacceptable loss of detection
rates and unacceptably large systematic biases in the estimated parameters.Comment: 11 pages, 9 figures, submitted to Phys. Rev.
Gravitational-wave data analysis using binary black-hole waveforms
Coalescing binary black-hole systems are among the most promising sources of
gravitational waves for ground-based interferometers. While the \emph{inspiral}
and \emph{ring-down} stages of the binary black-hole coalescence are
well-modelled by analytical approximation methods in general relativity, the
recent progress in numerical relativity has enabled us to compute accurate
waveforms from the \emph{merger} stage also. This has an important impact on
the search for gravitational waves from binary black holes. In particular,
while the current gravitational-wave searches look for each stage of the
coalescence separately, combining the results from analytical and numerical
relativity enables us to \emph{coherently} search for all three stages using a
single template family. `Complete' binary black-hole waveforms can now be
produced by matching post-Newtonian waveforms with those computed by numerical
relativity. These waveforms can be parametrised to produce analytical waveform
templates. The `complete' waveforms can also be used to estimate the efficiency
of different search methods aiming to detect signals from black-hole
coalescences. This paper summarises some recent efforts in this direction.Comment: Minor modifications in the text, added table of phenomenological
coefficient
Degeneracy of gravitational waveforms in the context of GW150914
We study the degeneracy of theoretical gravitational waveforms for binary
black hole mergers using an aligned-spin effective-one-body model. After
appropriate truncation, bandpassing, and matching, we identify regions in the
mass--spin parameter space containing waveforms similar to the template
proposed for GW150914, with masses and , using the cross-correlation coefficient as a measure of
the similarity between waveforms. Remarkably high cross-correlations are found
across broad regions of parameter space. The associated uncertanties exceed
these from LIGO's Bayesian analysis considerably. We have shown that waveforms
with greatly increased masses, such as and , and strong anti-aligned spins ( and )
yield almost the same signal-to-noise ratio in the strain data for GW150914.Comment: Accepted for publication in JCA
Comparison of post-Newtonian templates for compact binary inspiral signals in gravitational-wave detectors
The two-body dynamics in general relativity has been solved perturbatively
using the post-Newtonian (PN) approximation. The evolution of the orbital phase
and the emitted gravitational radiation are now known to a rather high order up
to O(v^8), v being the characteristic velocity of the binary. The orbital
evolution, however, cannot be specified uniquely due to the inherent freedom in
the choice of parameter used in the PN expansion as well as the method pursued
in solving the relevant differential equations. The goal of this paper is to
determine the (dis)agreement between different PN waveform families in the
context of initial and advanced gravitational-wave detectors. The waveforms
employed in our analysis are those that are currently used by Initial
LIGO/Virgo, that is the time-domain PN models TaylorT1, TaylorT2, TaylorT3,
TaylorT4 and TaylorEt, the effective one-body (EOB) model, and the
Fourier-domain representation TaylorF2. We examine the overlaps of these models
with one another and with the prototype effective one-body model (calibrated to
numerical relativity simulations, as currently used by initial LIGO) for a
number of different binaries at 2PN, 3PN and 3.5PN orders to quantify their
differences and to help us decide whether there exist preferred families that
are the most appropriate as search templates. We conclude that as long as the
total mass remains less than a certain upper limit M_crit, all template
families at 3.5PN order (except TaylorT3 and TaylorEt) are equally good for the
purpose of detection. The value of M_crit is found to be ~ 12M_Sun for Initial,
Enhanced and Advanced LIGO. From a purely computational point of view we
recommend that 3.5PN TaylorF2 be used below Mcrit and EOB calibrated to
numerical relativity simulations be used for total binary mass M > Mcrit.Comment: 27 pages, 8 figures, 4 tables, submitted to PR
Decodability Attack against the Fuzzy Commitment Scheme with Public Feature Transforms
The fuzzy commitment scheme is a cryptographic primitive that can be used to
store biometric templates being encoded as fixed-length feature vectors
protected. If multiple related records generated from the same biometric
instance can be intercepted, their correspondence can be determined using the
decodability attack. In 2011, Kelkboom et al. proposed to pass the feature
vectors through a record-specific but public permutation process in order to
prevent this attack. In this paper, it is shown that this countermeasure
enables another attack also analyzed by Simoens et al. in 2009 which can even
ease an adversary to fully break two related records. The attack may only be
feasible if the protected feature vectors have a reasonably small Hamming
distance; yet, implementations and security analyses must account for this
risk. This paper furthermore discusses that by means of a public
transformation, the attack cannot be prevented in a binary fuzzy commitment
scheme based on linear codes. Fortunately, such transformations can be
generated for the non-binary case. In order to still be able to protect binary
feature vectors, one may consider to use the improved fuzzy vault scheme by
Dodis et al. which may be secured against linkability attacks using
observations made by Merkle and Tams
Detecting gravitational waves from precessing binaries of spinning compact objects. II. Search implementation for low-mass binaries
Detection template families (DTFs) are built to capture the essential
features of true gravitational waveforms using a small set of phenomenological
waveform parameters. Buonanno, Chen, and Vallisneri [Phys. Rev. D 67, 104025
(2003)] proposed the ``BCV2'' DTF to perform computationally efficient searches
for signals from precessing binaries of compact stellar objects. Here we test
the signal-matching performance of the BCV2 DTF for asymmetric--mass-ratio
binaries, and specifically for double--black-hole binaries with component
masses (m1,m2): (6~12Msun, 1~3Msun), and for black-hole--neutron-star binaries
with component masses (m1,m2) = (10Msun, 1.4Msun); we take all black holes to
be maximally spinning. We find a satisfactory signal-matching performance, with
fitting factors averaging between 0.94 and 0.98. We also scope out the region
of BCV2 parameters needed for a template-based search, we evaluate the template
match metric, we discuss a template-placement strategy, and we estimate the
number of templates needed for searches at the LIGO design sensitivity. In
addition, after gaining more insight in the dynamics of spin--orbit precession,
we propose a modification of the BCV2 DTF that is parametrized by physical
(rather than phenomenological) parameters. We test this modified ``BCV2P'' DTF
for the (10Msun, 1.4Msun) black-hole--neutron-star system, finding a
signal-matching performance comparable to the BCV2 DTF, and a reliable
parameter-estimation capability for target-binary quantities such as the chirp
mass and the opening angle (the angle between the black-hole spin and the
orbital angular momentum).Comment: 18 pages, 15 figure
Learning about compact binary merger: the interplay between numerical relativity and gravitational-wave astronomy
Activities in data analysis and numerical simulation of gravitational waves
have to date largely proceeded independently. In this work we study how
waveforms obtained from numerical simulations could be effectively used within
the data analysis effort to search for gravitational waves from black hole
binaries. We propose measures to quantify the accuracy of numerical waveforms
for the purpose of data analysis and study how sensitive the analysis is to
errors in the waveforms. We estimate that ~100 templates (and ~10 simulations
with different mass ratios) are needed to detect waves from non-spinning binary
black holes with total masses in the range 100 Msun < M < 400 Msun using
initial LIGO. Of course, many more simulation runs will be needed to confirm
that the correct physics is captured in the numerical evolutions. From this
perspective, we also discuss sources of systematic errors in numerical waveform
extraction and provide order of magnitude estimates for the computational cost
of simulations that could be used to estimate the cost of parameter space
surveys. Finally, we discuss what information from near-future numerical
simulations of compact binary systems would be most useful for enhancing the
detectability of such events with contemporary gravitational wave detectors and
emphasize the role of numerical simulations for the interpretation of eventual
gravitational-wave observations.Comment: 19 pages, 12 figure
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