3,421 research outputs found
Gravitational wave burst vetoes in the LIGO S2 and S3 data analyses
The LIGO detectors collected about 4 months of data in 2003-2004 during two
science runs, S2 and S3. Several environmental and auxiliary channels that
monitor the instruments' physical environment and overall interferometric
operation were analyzed in order to establish the quality of the data as well
as the presence of transients of non-astrophysical origin. This analysis
allowed better understanding of the noise character of the instruments and the
establishment of correlations between transients in these channels and the one
recording the gravitational wave strain. In this way vetoes for spurious burst
were identified. We present the methodology we followed in this analysis and
the results from the S2 and S3 veto analysis within the context of the search
for gravitational wave bursts.Comment: 9 pages, 4 figures, submitted to Classical and Quantum Gravity for
the special issue of the GWDAW9 Proceeding
A burst search for gravitational waves from binary black holes
Compact binary coalescence (CBC) is one of the most promising sources of
gravitational waves. These sources are usually searched for with matched
filters which require accurate calculation of the GW waveforms and generation
of large template banks. We present a complementary search technique based on
algorithms used in un-modeled searches. Initially designed for detection of
un-modeled bursts, which can span a very large set of waveform morphologies,
the search algorithm presented here is constrained for targeted detection of
the smaller subset of CBC signals. The constraint is based on the assumption of
elliptical polarisation for signals received at the detector. We expect that
the algorithm is sensitive to CBC signals in a wide range of masses, mass
ratios, and spin parameters. In preparation for the analysis of data from the
fifth LIGO-Virgo science run (S5), we performed preliminary studies of the
algorithm on test data. We present the sensitivity of the search to different
types of simulated CBC waveforms. Also, we discuss how to extend the results of
the test run into a search over all of the current LIGO-Virgo data set.Comment: 12 pages, 4 figures, 2 tables, submitted for publication in CQG in
the special issue for the conference proceedings of GWDAW13; corrected some
typos, addressed some minor reviewer comments one section restructured and
references updated and correcte
Performance of the WaveBurst algorithm on LIGO data
In this paper we describe the performance of the WaveBurst algorithm which
was designed for detection of gravitational wave bursts in interferometric
data. The performance of the algorithm was evaluated on the test data set
collected during the second LIGO Scientific run. We have measured the false
alarm rate of the algorithm as a function of the threshold and estimated its
detection efficiency for simulated burst waveforms.Comment: proceedings of GWDAW, 2003 conference, 13 pages, 6 figure
Competition of Color Ferromagnetic and Superconductive States in a Quark-Gluon System
The possibility of color ferromagnetism in an SU(2) gauge field model is
investigated. The conditions allowing a stable color ferromagnetic state of the
quark system in the chromomagnetic field occupying small domains are
considered. A phase transition between this state and the color superconducting
state is considered. The effect of finite temperature is analyzed.Comment: 21 pages, 4 Postscript figure
Robust Bayesian detection of unmodelled bursts
A Bayesian treatment of the problem of detecting an unmodelled gravitational
wave burst with a global network of gravitational wave observatories reveals
that several previously proposed statistics have implicit biases that render
them sub-optimal for realistic signal populations.Comment: 9 pages, 1 figure, submitted to CQG Amaldi proceedings special issu
LIGO End-to-End simulation Program
A time-domain simulation program has been developed to provide an accurate description of interferometric gravitational wave detectors. This is being utilized to build a model of LIGO with the aim of aiding in the shakedown and integration of the interferometer subsystems, and ultimately the optimization of detector sensitivity
Diffraction dissociation in proton-proton collisions at = 0.9 TeV, 2.76 TeV and 7 TeV with ALICE at the LHC
The relative rates of single- and double- diffractive processes were measured
with the ALICE detector by studying properties of gaps in the pseudorapidity
distribution of particles produced in proton-proton collisions at =
0.9 TeV, 2.76 TeV and 7 TeV. ALICE triggering efficiencies are determined for
various classes of events, using a detector simulation validated with data on
inclusive particle production. Cross-sections are determined using van der Meer
scans to measure beam properties and obtain a measurement of the luminosity
Enhancing the significance of gravitational wave bursts through signal classification
The quest to observe gravitational waves challenges our ability to
discriminate signals from detector noise. This issue is especially relevant for
transient gravitational waves searches with a robust eyes wide open approach,
the so called all- sky burst searches. Here we show how signal classification
methods inspired by broad astrophysical characteristics can be implemented in
all-sky burst searches preserving their generality. In our case study, we apply
a multivariate analyses based on artificial neural networks to classify waves
emitted in compact binary coalescences. We enhance by orders of magnitude the
significance of signals belonging to this broad astrophysical class against the
noise background. Alternatively, at a given level of mis-classification of
noise events, we can detect about 1/4 more of the total signal population. We
also show that a more general strategy of signal classification can actually be
performed, by testing the ability of artificial neural networks in
discriminating different signal classes. The possible impact on future
observations by the LIGO-Virgo network of detectors is discussed by analysing
recoloured noise from previous LIGO-Virgo data with coherent WaveBurst, one of
the flagship pipelines dedicated to all-sky searches for transient
gravitational waves
Cooper pairing and finite-size effects in a NJL-type four-fermion model
Starting from a NJL-type model with N fermion species fermion and difermion
condensates and their associated phase structures are considered at nonzero
chemical potential and zero temperature in spaces with nontrivial
topology of the form and . Special
attention is devoted to the generation of the superconducting phase. In
particular, for the cases of antiperiodic and periodic boundary conditions we
have found that the critical curve of the phase transitions between the chiral
symmetry breaking and superconducting phases as well as the corresponding
condensates and particle densities strongly oscillate vs ,
where is the length of the circumference . Moreover, it is shown that
at some finite values of the superconducting phase transition is shifted to
smaller values both of and particle density in comparison with the case
of .Comment: 13 pages, 13 figures; minor changes; new references added; version
accepted to PR
Magnetic Susceptibility of the Quark Condensate and Polarization from Chiral Models
We compute the magnetic susceptibility of the quark condensate and the
polarization of quarks at zero temperature and in a uniform magnetic
background. Our theoretical framework consists of two chiral models that allow
to treat self-consistently the spontaneous breaking of chiral symmetry: the
linear model coupled to quarks, dubbed quark-meson model, and the
Nambu-Jona-Lasinio model. We also perform analytic estimates of the same
quantities within the renormalized quark-meson model, both in the regimes of
weak and strong fields. Our numerical results are in agreement with the recent
literature; moreover, we confirm previous Lattice findings, related to the
saturation of the polarization at large fields.Comment: 13 pages, 4 figure
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