9,077 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 on gravitational-wave signals based on loudest events
Searches for gravitational-wave bursts have often focused on the loudest
event(s) in searching for detections and in determining upper limits on
astrophysical populations. Typical upper limits have been reported on event
rates and event amplitudes which can then be translated into constraints on
astrophysical populations. We describe the mathematical construction of such
upper limits.Comment: 8 pages, 1 figur
A Micro-Analytical Technique for Determination of Aluminum in Aqueous Solutions
A flow-cell colorimetric technique has been developed by which Al concentrations of 0.0003to 0.1 wt. percent can be analyzed in one-microliter fluid samples.An A1-complexing reagent (Ferron) continuously flowing through teflon capillary tubing is spiked with one-microliter aliquots of solutions containing A1. The sample reacts with the reagent and subsequently passes through a microcolorimeter. Measurement of less than one nanomole A1 is possible by comparing the integrated absorbance of unknown samples with standard solutions
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
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.
Stability criterion for self-similar solutions with a scalar field and those with a stiff fluid in general relativity
A stability criterion is derived in general relativity for self-similar
solutions with a scalar field and those with a stiff fluid, which is a perfect
fluid with the equation of state . A wide class of self-similar
solutions turn out to be unstable against kink mode perturbation. According to
the criterion, the Evans-Coleman stiff-fluid solution is unstable and cannot be
a critical solution for the spherical collapse of a stiff fluid if we allow
sufficiently small discontinuity in the density gradient field in the initial
data sets. The self-similar scalar-field solution, which was recently found
numerically by Brady {\it et al.} (2002 {\it Class. Quantum. Grav.} {\bf 19}
6359), is also unstable. Both the flat Friedmann universe with a scalar field
and that with a stiff fluid suffer from kink instability at the particle
horizon scale.Comment: 15 pages, accepted for publication in Classical and Quantum Gravity,
typos correcte
Jamming transitions in a schematic model of suspension rheology
We study the steady-state response to applied stress in a simple scalar model
of sheared colloids. Our model is based on a schematic (F2) model of the glass
transition, with a memory term that depends on both stress and shear rate. For
suitable parameters, we find transitions from a fluid to a nonergodic, jammed
state, showing zero flow rate in an interval of applied stress. Although the
jammed state is a glass, we predict that jamming transitions have an analytical
structure distinct from that of the conventional mode coupling glass
transition. The static jamming transition we discuss is also distinct from
hydrodynamic shear thickening.Comment: 7 pages; 3 figures; improved version with added references. Accepted
for publication in Europhysics Letter
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