7,387 research outputs found
The Loudest Event Statistic: General Formulation, Properties and Applications
The use of the loudest observed event to generate statistical statements
about rate and strength has become standard in searches for gravitational waves
from compact binaries and pulsars. The Bayesian formulation of the method is
generalized in this paper to allow for uncertainties both in the background
estimate and in the properties of the population being constrained. The method
is also extended to allow rate interval construction. Finally, it is shown how
to combine the results from multiple experiments and a comparison is drawn
between the upper limit obtained in a single search and the upper limit
obtained by combining the results of two experiments each of half the original
duration. To illustrate this, we look at an example case, motivated by the
search for gravitational waves from binary inspiral.Comment: 11 pages, 8 figure
Upper Limits from Counting Experiments with Multiple Pipelines
In counting experiments, one can set an upper limit on the rate of a Poisson
process based on a count of the number of events observed due to the process.
In some experiments, one makes several counts of the number of events, using
different instruments, different event detection algorithms, or observations
over multiple time intervals. We demonstrate how to generalize the classical
frequentist upper limit calculation to the case where multiple counts of events
are made over one or more time intervals using several (not necessarily
independent) procedures. We show how different choices of the rank ordering of
possible outcomes in the space of counts correspond to applying different
levels of significance to the various measurements. We propose an ordering that
is matched to the sensitivity of the different measurement procedures and show
that in typical cases it gives stronger upper limits than other choices. As an
example, we show how this method can be applied to searches for
gravitational-wave bursts, where multiple burst-detection algorithms analyse
the same data set, and demonstrate how a single combined upper limit can be set
on the gravitational-wave burst rate.Comment: 26 pages (CQG style), 8 figures. Added study of robustness of limits
Numerical investigation of black hole interiors
Gravitational perturbations which are present in any realistic stellar
collapse to a black hole, die off in the exterior of the hole, but experience
an infinite blueshift in the interior. This is believed to lead to a slowly
contracting lightlike scalar curvature singularity, characterized by a
divergence of the hole's (quasi-local) mass function along the inner horizon.
The region near the inner horizon is described to great accuracy by a plane
wave spacetime. While Einstein's equations for this metric are still too
complicated to be solved in closed form it is relatively simple to integrate
them numerically.
We find for generic regular initial data the predicted mass inflation type
null singularity, rather than a spacelike singularity. It thus seems that mass
inflation indeed represents a generic self-consistent picture of the black hole
interior.Comment: 6 pages LaTeX, 3 eps figure
Data analysis of gravitational-wave signals from spinning neutron stars. IV. An all-sky search
We develop a set of data analysis tools for a realistic all-sky search for
continuous gravitational-wave signals. The methods that we present apply to
data from both the resonant bar detectors that are currently in operation and
the laser interferometric detectors that are in the final stages of
construction and commissioning. We show that with our techniques we shall be
able to perform an all-sky 2-day long coherent search of the narrow-band data
from the resonant bar EXPLORER with no loss of signals with the dimensionless
amplitude greater than .Comment: REVTeX, 26 pages, 1 figure, submitted to Phys. Rev.
Matching of the continuous gravitational wave in an all sky search
We investigate the matching of continuous gravitational wave (CGW) signals in
an all sky search with reference to Earth based laser interferometric
detectors. We consider the source location as the parameters of the signal
manifold and templates corresponding to different source locations. It has been
found that the matching of signals from locations in the sky that differ in
their co-latitude and longitude by radians decreases with source
frequency. We have also made an analysis with the other parameters affecting
the symmetries. We observe that it may not be relevant to take care of the
symmetries in the sky locations for the search of CGW from the output of
LIGO-I, GEO600 and TAMA detectors.Comment: 16 pages, 7 figures, 3 Tables, To appear in Int. J. Mod. Phys.
Gauge symmetry breaking on orbifolds
We discuss a new method for gauge symmetry breaking in theories with one
extra dimension compactified on the orbifold S^1/Z_2. If we assume that fields
and their derivatives can jump at the orbifold fixed points, we can implement a
generalized Scherk-Schwarz mechanism that breaks the gauge symmetry. We show
that our model with discontinuous fields is equivalent to another with
continuous but non periodic fields; in our scheme localized lagrangian terms
for bulk fields appear.Comment: 6 pages, 2 figures. Talk given at the XXXVIIth Rencontres de Moriond,
"Electroweak interactions and unified theories", Les Arcs, France, 9-16 Mar
2002. Minor changes, one reference adde
Odd-parity perturbations of self-similar Vaidya spacetime
We carry out an analytic study of odd-parity perturbations of the
self-similar Vaidya space-times that admit a naked singularity. It is found
that an initially finite perturbation remains finite at the Cauchy horizon.
This holds not only for the gauge invariant metric and matter perturbation, but
also for all the gauge invariant perturbed Weyl curvature scalars, including
the gravitational radiation scalars. In each case, `finiteness' refers to
Sobolev norms of scalar quantities on naturally occurring spacelike
hypersurfaces, as well as pointwise values of these quantities.Comment: 28 page
Incorporating information from source simulations into searches for gravitational-wave bursts
The detection of gravitational waves from astrophysical sources of
gravitational waves is a realistic goal for the current generation of
interferometric gravitational-wave detectors. Short duration bursts of
gravitational waves from core-collapse supernovae or mergers of binary black
holes may bring a wealth of astronomical and astrophysical information. The
weakness of the waves and the rarity of the events urges the development of
optimal methods to detect the waves. The waves from these sources are not
generally known well enough to use matched filtering however; this drives the
need to develop new ways to exploit source simulation information in both
detections and information extraction. We present an algorithmic approach to
using catalogs of gravitational-wave signals developed through numerical
simulation, or otherwise, to enhance our ability to detect these waves. As more
detailed simulations become available, it is straightforward to incorporate the
new information into the search method. This approach may also be useful when
trying to extract information from a gravitational-wave observation by allowing
direct comparison between the observation and simulations.Comment: 8 pages, 1 figur
Size Gap for Zero Temperature Black Holes in Semiclassical Gravity
We show that a gap exists in the allowed sizes of all zero temperature static
spherically symmetric black holes in semiclassical gravity when only
conformally invariant fields are present. The result holds for both charged and
uncharged black holes. By size we mean the proper area of the event horizon.
The range of sizes that do not occur depends on the numbers and types of
quantized fields that are present. We also derive some general properties that
both zero and nonzero temperature black holes have in all classical and
semiclassical metric theories of gravity.Comment: 4 pages, ReVTeX, no figure
The Real Scalar Field in Schwarzschild-de Sitter Spacetime
In this paper, the real scalar field equation in Schwarzschild-de Sitter
spacetime is solved numerically with high precision. A method called polynomial
approximation is introduced to derive the relation between the tortoise
coordinate x and the radius r. This method is different from the tangent
approximation [1] and leads to more accurate result. The Nariai black hole is
then discussed in details. We find that the wave function is harmonic only near
the horizons as I. Brevik and B. Simonsen [1] found. Howerver the wave function
is not harmonic in the region of the potential peak, with amplitude increasing
instead. Furthermore, we also find that, when cosmological constant decreases,
the potential peak increases, and the maximum wave amplitude increases.Comment: 11 pages, 5 figures. To be published in volume 35(2003), G.R.
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