2,714 research outputs found
Mapping the gravitational wave background
The gravitational wave sky is expected to have isolated bright sources
superimposed on a diffuse gravitational wave background. The background
radiation has two components: a confusion limited background from unresolved
astrophysical sources; and a cosmological component formed during the birth of
the universe. A map of the gravitational wave background can be made by
sweeping a gravitational wave detector across the sky. The detector output is a
complicated convolution of the sky luminosity distribution, the detector
response function and the scan pattern. Here we study the general
de-convolution problem, and show how LIGO (Laser Interferometric Gravitational
Observatory) and LISA (Laser Interferometer Space Antenna) can be used to
detect anisotropies in the gravitational wave background.Comment: 16 pages, 6 figures. Submitted to CQ
Searching for Massive Black Hole Binaries in the first Mock LISA Data Challenge
The Mock LISA Data Challenge is a worldwide effort to solve the LISA data
analysis problem. We present here our results for the Massive Black Hole Binary
(BBH) section of Round 1. Our results cover Challenge 1.2.1, where the
coalescence of the binary is seen, and Challenge 1.2.2, where the coalescence
occurs after the simulated observational period. The data stream is composed of
Gaussian instrumental noise plus an unknown BBH waveform. Our search algorithm
is based on a variant of the Markov Chain Monte Carlo method that uses
Metropolis-Hastings sampling and thermostated frequency annealing. We present
results from the training data sets and the blind data sets. We demonstrate
that our algorithm is able to rapidly locate the sources, accurately recover
the source parameters, and provide error estimates for the recovered
parameters.Comment: 11 pages, 6 figures, Submitted to CQG proceedings of GWDAW 11, AEI,
Germany, Dec 200
Non-Singular Gravity Without Black Holes
A non-singular, static spherically symmetric solution to the nonsymmetric
gravitational and electromagnetic theory field equations is derived, which
depends on the four parameters m, l^2, Q and s, where m is the mass, Q is the
electric charge, l^2 is the NGT charge of a body and s is a dimensionless
constant. The electromagnetic field invariants are also singularity-free, so
that it is possible to construct regular particle-like solutions in the theory.
All the curvature invariants are finite, there are no null surfaces in the
spacetime and there are no black holes. A new stable, superdense object (SDO)
replaces black holes.Comment: 26 pages, UTPT-94-0
Facing the LISA Data Analysis Challenge
By being the first observatory to survey the source rich low frequency region
of the gravitational wave spectrum, the Laser Interferometer Space Antenna
(LISA) will revolutionize our understanding of the Cosmos. For the first time
we will be able to detect the gravitational radiation from millions of galactic
binaries, the coalescence of two massive black holes, and the inspirals of
compact objects into massive black holes. The signals from multiple sources in
each class, and possibly others as well, will be simultaneously present in the
data. To achieve the enormous scientific return possible with LISA,
sophisticated data analysis techniques must be developed which can mine the
complex data in an effort to isolate and characterize individual signals. This
proceedings paper very briefly summarizes the challenges associated with
analyzing the LISA data, the current state of affairs, and the necessary next
steps to move forward in addressing the imminent challenges.Comment: 4 pages, no figures, Proceedings paper for the TeV Particle
Astrophysics II conference held Aug 28-31 at the Univ. of Wisconsi
Detecting the Cosmic Gravitational Wave Background with the Big Bang Observer
The detection of the Cosmic Microwave Background Radiation (CMB) was one of
the most important cosmological discoveries of the last century. With the
development of interferometric gravitational wave detectors, we may be in a
position to detect the gravitational equivalent of the CMB in this century. The
Cosmic Gravitational Background (CGB) is likely to be isotropic and stochastic,
making it difficult to distinguish from instrument noise. The contribution from
the CGB can be isolated by cross-correlating the signals from two or more
independent detectors. Here we extend previous studies that considered the
cross-correlation of two Michelson channels by calculating the optimal signal
to noise ratio that can be achieved by combining the full set of interferometry
variables that are available with a six link triangular interferometer. In
contrast to the two channel case, we find that the relative orientation of a
pair of coplanar detectors does not affect the signal to noise ratio. We apply
our results to the detector design described in the Big Bang Observer (BBO)
mission concept study and find that BBO could detect a background with
.Comment: 15 pages, 12 Figure
Using the acoustic peak to measure cosmological parameters
Recent measurements of the cosmic microwave background radiation by the
Boomerang experiment indicate that the universe is spatially flat. Here some
simple back-of-the-envelope calculations are used to explain their result. The
main result is a simple formula for the angular scale of the acoustic peak in
terms of the standard cosmological parameters:
l=193*[1+3(1-Omega_0)/5+(1-h)/5+Omega_Lambda/35].Comment: 4 pages, 1 figure, Explanations have been clarifie
Forward Modeling of Space-borne Gravitational Wave Detectors
Planning is underway for several space-borne gravitational wave observatories
to be built in the next ten to twenty years. Realistic and efficient forward
modeling will play a key role in the design and operation of these
observatories. Space-borne interferometric gravitational wave detectors operate
very differently from their ground based counterparts. Complex orbital motion,
virtual interferometry, and finite size effects complicate the description of
space-based systems, while nonlinear control systems complicate the description
of ground based systems. Here we explore the forward modeling of space-based
gravitational wave detectors and introduce an adiabatic approximation to the
detector response that significantly extends the range of the standard low
frequency approximation. The adiabatic approximation will aid in the
development of data analysis techniques, and improve the modeling of
astrophysical parameter extraction.Comment: 14 Pages, 14 Figures, RevTex
Chaotic Scattering and Capture of Strings by Black Hole
We consider scattering and capture of circular cosmic strings by a
Schwarzschild black hole. Although being a priori a very simple axially
symmetric two-body problem, it shows all the features of chaotic scattering. In
particular, it contains a fractal set of unstable periodic solutions; a
so-called strange repellor. We study the different types of trajectories and
obtain the fractal dimension of the basin-boundary separating the space of
initial conditions according to the different asymptotic outcomes. We also
consider the fractal dimension as a function of energy, and discuss the
transition from order to chaos.Comment: RevTeX 3.1, 9 pages, 5 figure
Time-frequency analysis of extreme-mass-ratio inspiral signals in mock LISA data
Extreme-mass-ratio inspirals (EMRIs) of ~ 1-10 solar-mass compact objects
into ~ million solar-mass massive black holes can serve as excellent probes of
strong-field general relativity. The Laser Interferometer Space Antenna (LISA)
is expected to detect gravitational wave signals from apprxomiately one hundred
EMRIs per year, but the data analysis of EMRI signals poses a unique set of
challenges due to their long duration and the extensive parameter space of
possible signals. One possible approach is to carry out a search for EMRI
tracks in the time-frequency domain. We have applied a time-frequency search to
the data from the Mock LISA Data Challenge (MLDC) with promising results. Our
analysis used the Hierarchical Algorithm for Clusters and Ridges to identify
tracks in the time-frequency spectrogram corresponding to EMRI sources. We then
estimated the EMRI source parameters from these tracks. In these proceedings,
we discuss the results of this analysis of the MLDC round 1.3 data.Comment: Amaldi-7 conference proceedings; requires jpconf style file
- …