23 research outputs found
A stochastic template placement algorithm for gravitational wave data analysis
This paper presents an algorithm for constructing matched-filter template
banks in an arbitrary parameter space. The method places templates at random,
then removes those which are "too close" together. The properties and
optimality of stochastic template banks generated in this manner are
investigated for some simple models. The effectiveness of these template banks
for gravitational wave searches for binary inspiral waveforms is also examined.
The properties of a stochastic template bank are then compared to the
deterministically placed template banks that are currently used in
gravitational wave data analysis.Comment: 14 pages, 11 figure
Parametrized tests of post-Newtonian theory using Advanced LIGO and Einstein Telescope
General relativity has very specific predictions for the gravitational
waveforms from inspiralling compact binaries obtained using the post-Newtonian
(PN) approximation. We investigate the extent to which the measurement of the
PN coefficients, possible with the second generation gravitationalwave
detectors such as the Advanced Laser Interferometer Gravitational-Wave
Observatory (LIGO) and the third generation gravitational-wave detectors such
as the Einstein Telescope (ET), could be used to test post-Newtonian theory and
to put bounds on a subclass of parametrized-post-Einstein theories which differ
from general relativity in a parametrized sense. We demonstrate this
possibility by employing the best inspiralling waveform model for nonspinning
compact binaries which is 3.5PN accurate in phase and 3PN in amplitude. Within
the class of theories considered, Advanced LIGO can test the theory at 1.5PN
and thus the leading tail term. Future observations of stellar mass black hole
binaries by ET can test the consistency between the various PN coefficients in
the gravitational-wave phasing over the mass range of 11-44 Msun. The choice of
the lower frequency cut off is important for testing post-Newtonian theory
using the ET. The bias in the test arising from the assumption of nonspinning
binaries is indicated.Comment: 18 pages, 11 figures, Matches with the published versio
Gravitational Wave Chirp Search: Economization of PN Matched Filter Bank via Cardinal Interpolation
The final inspiral phase in the evolution of a compact binary consisting of
black holes and/or neutron stars is among the most probable events that a
network of ground-based interferometric gravitational wave detectors is likely
to observe. Gravitational radiation emitted during this phase will have to be
dug out of noise by matched-filtering (correlating) the detector output with a
bank of several templates, making the computational resources required
quite demanding, though not formidable. We propose an interpolation method for
evaluating the correlation between template waveforms and the detector output
and show that the method is effective in substantially reducing the number of
templates required. Indeed, the number of templates needed could be a factor
smaller than required by the usual approach, when the minimal overlap
between the template bank and an arbitrary signal (the so-called {\it minimal
match}) is 0.97. The method is amenable to easy implementation, and the various
detector projects might benefit by adopting it to reduce the computational
costs of inspiraling neutron star and black hole binary search.Comment: scheduled for publicatin on Phys. Rev. D 6
Correlator Bank Detection of GW chirps. False-Alarm Probability, Template Density and Thresholds: Behind and Beyond the Minimal-Match Issue
The general problem of computing the false-alarm rate vs. detection-threshold
relationship for a bank of correlators is addressed, in the context of
maximum-likelihood detection of gravitational waves, with specific reference to
chirps from coalescing binary systems. Accurate (lower-bound) approximants for
the cumulative distribution of the whole-bank supremum are deduced from a class
of Bonferroni-type inequalities. The asymptotic properties of the cumulative
distribution are obtained, in the limit where the number of correlators goes to
infinity. The validity of numerical simulations made on small-size banks is
extended to banks of any size, via a gaussian-correlation inequality. The
result is used to estimate the optimum template density, yielding the best
tradeoff between computational cost and detection efficiency, in terms of
undetected potentially observable sources at a prescribed false-alarm level,
for the simplest case of Newtonian chirps.Comment: submitted to Phys. Rev.
Data analysis of gravitational-wave signals from spinning neutron stars. III. Detection statistics and computational requirements
We develop the analytic and numerical tools for data analysis of the
gravitational-wave signals from spinning neutron stars for ground-based laser
interferometric detectors. We study in detail the statistical properties of the
optimum functional that need to be calculated in order to detect the
gravitational-wave signal from a spinning neutron star and estimate its
parameters. We derive formulae for false alarm and detection probabilities both
for the optimal and the suboptimal filters. We assess the computational
requirements needed to do the signal search. We compare a number of criteria to
build sufficiently accurate templates for our data analysis scheme. We verify
the validity of our concepts and formulae by means of the Monte Carlo
simulations. We present algorithms by which one can estimate the parameters of
the continuous signals accurately.Comment: LaTeX, 45 pages, 13 figures, submitted to Phys. Rev.
On Estimation of the Post-Newtonian Parameters in the Gravitational-Wave Emission of a Coalescing Binary
The effect of the recently obtained 2nd post-Newtonian corrections on the
accuracy of estimation of parameters of the gravitational-wave signal from a
coalescing binary is investigated. It is shown that addition of this correction
degrades considerably the accuracy of determination of individual masses of the
members of the binary. However the chirp mass and the time parameter in the
signal is still determined to a very good accuracy. The possibility of
estimation of effects of other theories of gravity is investigated. The
performance of the Newtonian filter is investigated and it is compared with
performance of post-Newtonian search templates introduced recently. It is shown
that both search templates can extract accurately useful information about the
binary.Comment: 34 pages, 118Kb, LATEX format, submitted to Phys. Rev.
Bayesian Bounds on Parameter Estimation Accuracy for Compact Coalescing Binary Gravitational Wave Signals
A global network of laser interferometric gravitational wave detectors is
projected to be in operation by around the turn of the century. Here, the noisy
output of a single instrument is examined. A gravitational wave is assumed to
have been detected in the data and we deal with the subsequent problem of
parameter estimation. Specifically, we investigate theoretical lower bounds on
the minimum mean-square errors associated with measuring the parameters of the
inspiral waveform generated by an orbiting system of neutron stars/black holes.
Three theoretical lower bounds on parameter estimation accuracy are considered:
the Cramer-Rao bound (CRB); the Weiss-Weinstein bound (WWB); and the Ziv-Zakai
bound (ZZB). We obtain the WWB and ZZB for the Newtonian-form of the coalescing
binary waveform, and compare them with published CRB and numerical Monte-Carlo
results. At large SNR, we find that the theoretical bounds are all identical
and are attained by the Monte-Carlo results. As SNR gradually drops below 10,
the WWB and ZZB are both found to provide increasingly tighter lower bounds
than the CRB. However, at these levels of moderate SNR, there is a significant
departure between all the bounds and the numerical Monte-Carlo results.Comment: 17 pages (LaTeX), 4 figures. Submitted to Physical Review
Neuroticism-related personality traits are associated with posttraumatic stress after abortion : findings from a Swedish multi-center cohort study
Background: Most women who choose to terminate a pregnancy cope well following an abortion, although some women experience severe psychological distress. The general interpretation in the field is that the most consistent predictor of mental disorders after induced abortion is the mental health issues that women present with prior to the abortion. We have previously demonstrated that few women develop posttraumatic stress disorder (PTSD) or posttraumatic stress symptoms (PTSS) after induced abortion. Neuroticism is one predictor of importance for PTSD, and may thus be relevant as a risk factor for the development of PTSD or PTSS after abortion. We therefore compared Neuroticism-related personality trait scores of women who developed PTSD or PTSS after abortion to those of women with no evidence of PTSD or PTSS before or after the abortion. Methods: A Swedish multi-center cohort study including six Obstetrics and Gynecology Departments, where 1294 abortion-seeking women were included. The Screen Questionnaire-Posttraumatic Stress Disorder (SQ-PTSD) was used to evaluate PTSD and PTSS. Measurements were made at the first visit and at three and six month after the abortion. The Swedish universities Scales of Personality (SSP) was used for assessment of Neuroticism-related personality traits. Multiple logistic regression analyses were performed to investigate the risk factors for development of PTSD or PTSS post abortion. Results: Women who developed PTSD or PTSS after the abortion had higher scores than the comparison group on several of the personality traits associated with Neuroticism, specifically Somatic Trait Anxiety, Psychic Trait Anxiety, Stress Susceptibility and Embitterment. Women who reported high, or very high, scores on Neuroticism had adjusted odds ratios for PTSD/PTSS development of 2.6 (CI 95% 1.2-5.6) and 2.9 (CI 95% 1.3-6.6), respectively. Conclusion: High scores on Neuroticism-related personality traits influence the risk of PTSD or PTSS post abortion. This finding supports the argument that the most consistent predictor of mental disorders after abortion is pre-existing mental health status