34,868 research outputs found
The effect of different eLISA-like configurations on massive black hole parameter estimation
As the theme for the future L3 Cosmic Vision mission, ESA has recently chosen
the `Gravitational Wave Universe'. Within this call, a mission concept called
eLISA has been proposed. This observatory has a current initial configuration
consisting of 4 laser links between the three satellites, which are separated
by a distance of one million kilometers, constructing a single channel
Michelson interferometer. However, the final configuration for the observatory
will not be fixed until the end of this decade. With this in mind, we
investigate the effect of different eLISA-like configurations on massive black
hole detections. This work compares the results of a Bayesian inference study
of 120 massive black hole binaries out to a redshift of for a m
arm-length eLISA with four and six links, as well as a m
arm-length observatory with four links. We demonstrate that the original eLISA
configuration should allow us to recover the luminosity distance of the source
with an error of less than 10% out to a redshift of , and a sky error
box of out to . In contrast, both alternative
configurations suggest that we should be able to conduct the same parameter
recovery with errors of less than 10% in luminosity distance out to
and out to . Using the information from these
studies, we also infer that if we were able to construct a 2Gm, 6-link
detector, the above values would shift to for luminosity distance and
for sky error. While the final configuration will also be dependent
on both technological and financial considerations, our study suggests that
increasing the size of a two arm detector is a viable alternative to the
inclusion of a third arm in a smaller detector. More importantly, this work
further suggests no clear scientific loss between either choice.Comment: 9 pages, 5 figure
An Overview of LISA Data Analysis Algorithms
The development of search algorithms for gravitational wave sources in the
LISA data stream is currently a very active area of research. It has become
clear that not only does difficulty lie in searching for the individual
sources, but in the case of galactic binaries, evaluating the fidelity of
resolved sources also turns out to be a major challenge in itself. In this
article we review the current status of developed algorithms for galactic
binary, non-spinning supermassive black hole binary and extreme mass ratio
inspiral sources. While covering the vast majority of algorithms, we will
highlight those that represent the state of the art in terms of speed and
accuracy.Comment: 21 pages. Invited highlight article appearing in issue 01 of
Gravitational Waves Notes, "GW Notes", edited by Pau Amaro-Seoane and Bernard
F. Schutz at: http://brownbag.lisascience.org/lisa-gw-notes
Multiplicities and particle production at LEP
Recent results on hadron multiplicities in heavy and light quark
fragmentation above the Z peak (OPAL), and multiplicity distribution analysis
(L3) and inclusive f_1 production (DELPHI) in hadronic Z decays are presented.Comment: 3 pages, 4 figs. Talk given at the International Europhysics
Conference on High Energy Physics, EPS-HEP2003, 17-23 July 2003, Aachen,
German
Multiplicities and Correlations at LEP
A brief review on recent charge multiplicity and correlation measurements at
LEP is given. The measurements of unbiased gluon jet multiplicity are
discussed. Recent results on charged particle Bose-Einstein and Fermi-Dirac
correlations at LEP1 are reported. New results on two-particle correlations of
neutral pions are given. Correlations of more than two particles (high-order
correlations) obtained using different methods are performed. Recent
Bose-Einstein correlation measurements at LEP2 are discussed.Comment: 5 pages. Invited talk presented at the Xth International Workshop on
Deep Inelastic Scattering (DIS2002), Cracow, 30 April - 4 May 200
Intermittency and Correlations at LEP and at HERA
A review on recent investigations of local fluctuations and genuine
correlations in electron-positron annihilations at LEP and in positron-proton
collisions at HERA is given.Comment: Invited talk given at the XXXth Int. Symposium on Multiparticle
Dynamics (ISMD 2000), 9-15 October 2000, Tihany, Lake Balaton, Hungar
Detecting compact galactic binaries using a hybrid swarm-based algorithm
Compact binaries in our galaxy are expected to be one of the main sources of
gravitational waves for the future eLISA mission. During the mission lifetime,
many thousands of galactic binaries should be individually resolved. However,
the identification of the sources, and the extraction of the signal parameters
in a noisy environment are real challenges for data analysis. So far,
stochastic searches have proven to be the most successful for this problem. In
this work we present the first application of a swarm-based algorithm combining
Particle Swarm Optimization and Differential Evolution. These algorithms have
been shown to converge faster to global solutions on complicated likelihood
surfaces than other stochastic methods. We first demonstrate the effectiveness
of the algorithm for the case of a single binary in a 1 mHz search bandwidth.
This interesting problem gave the algorithm plenty of opportunity to fail, as
it can be easier to find a strong noise peak rather than the signal itself.
After a successful detection of a fictitious low-frequency source, as well as
the verification binary RXJ0806.3+1527, we then applied the algorithm to the
detection of multiple binaries, over different search bandwidths, in the cases
of low and mild source confusion. In all cases, we show that we can
successfully identify the sources, and recover the true parameters within a
99\% credible interval.Comment: 19 pages, 5 figure
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