6,265 research outputs found
The ACIGA Data Analysis programme
The Data Analysis programme of the Australian Consortium for Interferometric
Gravitational Astronomy (ACIGA) was set up in 1998 by the first author to
complement the then existing ACIGA programmes working on suspension systems,
lasers and optics, and detector configurations. The ACIGA Data Analysis
programme continues to contribute significantly in the field; we present an
overview of our activities.Comment: 10 pages, 0 figures, accepted, Classical and Quantum Gravity,
(Proceedings of the 5th Edoardo Amaldi Conference on Gravitational Waves,
Tirrenia, Pisa, Italy, 6-11 July 2003
Developments in GRworkbench
The software tool GRworkbench is an ongoing project in visual, numerical
General Relativity at The Australian National University. Recently, GRworkbench
has been significantly extended to facilitate numerical experimentation in
analytically-defined space-times. The numerical differential geometric engine
has been rewritten using functional programming techniques, enabling objects
which are normally defined as functions in the formalism of differential
geometry and General Relativity to be directly represented as function
variables in the C++ code of GRworkbench. The new functional differential
geometric engine allows for more accurate and efficient visualisation of
objects in space-times and makes new, efficient computational techniques
available. Motivated by the desire to investigate a recent scientific claim
using GRworkbench, new tools for numerical experimentation have been
implemented, allowing for the simulation of complex physical situations.Comment: 14 pages. To appear A. Moylan, S.M. Scott and A.C. Searle,
Developments in GRworkbench. Proceedings of the Tenth Marcel Grossmann
Meeting on General Relativity, editors M. Novello, S. Perez-Bergliaffa and R.
Ruffini. Singapore: World Scientific 200
Network sensitivity to geographical configuration
Gravitational wave astronomy will require the coordinated analysis of data
from the global network of gravitational wave observatories. Questions of how
to optimally configure the global network arise in this context. We have
elsewhere proposed a formalism which is employed here to compare different
configurations of the network, using both the coincident network analysis
method and the coherent network analysis method. We have constructed a network
model to compute a figure-of-merit based on the detection rate for a population
of standard-candle binary inspirals. We find that this measure of network
quality is very sensitive to the geographic location of component detectors
under a coincident network analysis, but comparatively insensitive under a
coherent network analysis.Comment: 7 pages, 4 figures, accepted for proceedings of the 4th Edoardo
Amaldi conference, incorporated referees' suggestions and corrected diagra
Targeted search for continuous gravitational waves: Bayesian versus maximum-likelihood statistics
We investigate the Bayesian framework for detection of continuous
gravitational waves (GWs) in the context of targeted searches, where the phase
evolution of the GW signal is assumed to be known, while the four amplitude
parameters are unknown. We show that the orthodox maximum-likelihood statistic
(known as F-statistic) can be rediscovered as a Bayes factor with an unphysical
prior in amplitude parameter space. We introduce an alternative detection
statistic ("B-statistic") using the Bayes factor with a more natural amplitude
prior, namely an isotropic probability distribution for the orientation of GW
sources. Monte-Carlo simulations of targeted searches show that the resulting
Bayesian B-statistic is more powerful in the Neyman-Pearson sense (i.e. has a
higher expected detection probability at equal false-alarm probability) than
the frequentist F-statistic.Comment: 12 pages, presented at GWDAW13, to appear in CQ
Using sports infrastructure to deliver economic and social change: Lessons for London beyond 2012
Over the last two decades, there has been a
new trend emerging within sport, which has
seen a shift, from investment for the sake of
sport, to investment in sport for good (Sport
England, 2008). In the context of the latter
approach, there has been an emergence of
the use of sport to address regeneration objectives,
largely stemming from the belief of government
and other sporting and non-sporting
organizations, that it can confer a wide range
of economic and social benefits to individuals
and communities beyond those of a purely
physical sporting nature, and can contribute
positively to the revitalization of declining
urban areas (BURA, 2003). This commentary
will examine regeneration legacy in the context
of the London Olympic Games. In particular,
it will focus on the use of sports stadia
as a tool for delivering economic and social
change, and by drawing upon previous examples,
suggest lessons London can learn to
enhance regeneration legacies beyond 2012
Real Time Relativity: exploration learning of special relativity
Real Time Relativity is a computer program that lets students fly at
relativistic speeds though a simulated world populated with planets, clocks,
and buildings. The counterintuitive and spectacular optical effects of
relativity are prominent, while systematic exploration of the simulation allows
the user to discover relativistic effects such as length contraction and the
relativity of simultaneity. We report on the physics and technology
underpinning the simulation, and our experience using it for teaching special
relativity to first year university students
Singular value decomposition applied to compact binary coalescence gravitational-wave signals
We investigate the application of the singular value decomposition to
compact-binary, gravitational-wave data-analysis. We find that the truncated
singular value decomposition reduces the number of filters required to analyze
a given region of parameter space of compact binary coalescence waveforms by an
order of magnitude with high reconstruction accuracy. We also compute an
analytic expression for the expected signal-loss due to the singular value
decomposition truncation.Comment: 4 figures, 6 page
Spectral Line Removal in the LIGO Data Analysis System (LDAS)
High power in narrow frequency bands, spectral lines, are a feature of an
interferometric gravitational wave detector's output. Some lines are coherent
between interferometers, in particular, the 2 km and 4 km LIGO Hanford
instruments. This is of concern to data analysis techniques, such as the
stochastic background search, that use correlations between instruments to
detect gravitational radiation. Several techniques of `line removal' have been
proposed. Where a line is attributable to a measurable environmental
disturbance, a simple linear model may be fitted to predict, and subsequently
subtract away, that line. This technique has been implemented (as the command
oelslr) in the LIGO Data Analysis System (LDAS). We demonstrate its application
to LIGO S1 data.Comment: 11 pages, 5 figures, to be published in CQG GWDAW02 proceeding
A holistic multi-scale approach to using 3D scanning technology in accident reconstruction
Three-dimensional scanning and documentation methods are becoming increasingly employed by law enforcement personnel for crime scene and accident scene recording. Three-dimensional documentation of the victim’s body in such cases is also increasingly used as the field of forensic radiology and imaging is expanding rapidly. These scanning technologies enable a more complete and detailed documentation than standard autopsy. This was used to examine a fatal pedestrian-vehicle collision where the pedestrian was killed by a van whilst crossing the road. Two competing scenarios were considered for the vehicle speed calculation: the pedestrian being projected forward by the impact or the pedestrian being carried on the vehicle’s bonnet. In order to assist with this, the impact area of the accident vehicle was scanned using laser surface scanning, the victim was scanned using postmortem CT and micro-CT and the data sets were combined to virtually match features of the vehicle to injuries on the victim. Micro-CT revealed additional injuries not previously detected, lending support to the pedestrian-carry theory
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