1,332 research outputs found
Gravitational-Wave Astronomy with Inspiral Signals of Spinning Compact-Object Binaries
Inspiral signals from binary compact objects (black holes and neutron stars)
are primary targets of the ongoing searches by ground-based gravitational-wave
interferometers (LIGO, Virgo, GEO-600 and TAMA-300). We present
parameter-estimation simulations for inspirals of black-hole--neutron-star
binaries using Markov-chain Monte-Carlo methods. For the first time, we have
both estimated the parameters of a binary inspiral source with a spinning
component and determined the accuracy of the parameter estimation, for
simulated observations with ground-based gravitational-wave detectors. We
demonstrate that we can obtain the distance, sky position, and binary
orientation at a higher accuracy than previously suggested in the literature.
For an observation of an inspiral with sufficient spin and two or three
detectors we find an accuracy in the determination of the sky position of
typically a few tens of square degrees.Comment: v2: major conceptual changes, 4 pages, 1 figure, 1 table, submitted
to ApJ
The universality of synchrony: critical behavior in a discrete model of stochastic phase coupled oscillators
We present the simplest discrete model to date that leads to synchronization
of stochastic phase-coupled oscillators. In the mean field limit, the model
exhibits a Hopf bifurcation and global oscillatory behavior as coupling crosses
a critical value. When coupling between units is strictly local, the model
undergoes a continuous phase transition which we characterize numerically using
finite-size scaling analysis. In particular, the onset of global synchrony is
marked by signatures of the XY universality class, including the appropriate
classical exponents and , a lower critical dimension ,
and an upper critical dimension .Comment: 4 pages, 4 figure
Parametric phase transition in one dimension
We calculate analytically the phase boundary for a nonequilibrium phase
transition in a one-dimensional array of coupled, overdamped parametric
harmonic oscillators in the limit of strong and weak spatial coupling. Our
results show that the transition is reentrant with respect to the spatial
coupling in agreement with the prediction of the mean field theory.Comment: to appear in Europhysics letter
Critical behavior and synchronization of discrete stochastic phase coupled oscillators
Synchronization of stochastic phase-coupled oscillators is known to occur but
difficult to characterize because sufficiently complete analytic work is not
yet within our reach, and thorough numerical description usually defies all
resources. We present a discrete model that is sufficiently simple to be
characterized in meaningful detail. In the mean field limit, the model exhibits
a supercritical Hopf bifurcation and global oscillatory behavior as coupling
crosses a critical value. When coupling between units is strictly local, the
model undergoes a continuous phase transition which we characterize numerically
using finite-size scaling analysis. In particular, we explicitly rule out
multistability and show that that the onset of global synchrony is marked by
signatures of the XY universality class. Our numerical results cover dimensions
d=2, 3, 4, and 5 and lead to the appropriate XY classical exponents \beta and
\nu, a lower critical dimension d_{lc} = 2, and an upper critical dimension
d_{uc}=4
Velocity Correlations, Diffusion and Stochasticity in a One-Dimensional System
We consider the motion of a test particle in a one-dimensional system of
equal-mass point particles. The test particle plays the role of a microscopic
"piston" that separates two hard-point gases with different concentrations and
arbitrary initial velocity distributions. In the homogeneous case when the
gases on either side of the piston are in the same macroscopic state, we
compute and analyze the stationary velocity autocorrelation function C(t).
Explicit expressions are obtained for certain typical velocity distributions,
serving to elucidate in particular the asymptotic behavior of C(t). It is shown
that the occurrence of a non-vanishing probability mass at zero velocity is
necessary for the occurrence of a long-time tail in C(t). The conditions under
which this is a tail are determined. Turning to the inhomogeneous
system with different macroscopic states on either side of the piston, we
determine its effective diffusion coefficient from the asymptotic behavior of
the variance of its position, as well as the leading behavior of the other
moments about the mean. Finally, we present an interpretation of the effective
noise arising from the dynamics of the two gases, and thence that of the
stochastic process to which the position of any particle in the system reduces
in the thermodynamic limit.Comment: 22 files, 2 eps figures. Submitted to PR
Noise induced transition from an absorbing phase to a regime of stochastic spatiotemporal intermittency
We introduce a stochastic partial differential equation capable of
reproducing the main features of spatiotemporal intermittency (STI).
Additionally the model displays a noise induced transition from laminarity to
the STI regime. We show by numerical simulations and a mean-field analysis that
for high noise intensities the system globally evolves to a uniform absorbing
phase, while for noise intensities below a critical value spatiotemporal
intermittence dominates. A quantitative computation of the loci of this
transition in the relevant parameter space is presented.Comment: 4 pages, 6 eps figures. Submitted to Phys. Rev. Lett. See for
additional information http://imedea.uib.es
Binary black hole spectroscopy
We study parameter estimation with post-Newtonian (PN) gravitational
waveforms for the quasi-circular, adiabatic inspiral of spinning binary compact
objects. The performance of amplitude-corrected waveforms is compared with that
of the more commonly used restricted waveforms, in Advanced LIGO and EGO. With
restricted waveforms, the properties of the source can only be extracted from
the phasing. For amplitude-corrected waveforms, the spectrum encodes a wealth
of additional information, which leads to dramatic improvements in parameter
estimation. At distances of Mpc, the full PN waveforms allow for
high-accuracy parameter extraction for total mass up to several hundred solar
masses, while with the restricted ones the errors are steep functions of mass,
and accurate parameter estimation is only possible for relatively light stellar
mass binaries. At the low-mass end, the inclusion of amplitude corrections
reduces the error on the time of coalescence by an order of magnitude in
Advanced LIGO and a factor of 5 in EGO compared to the restricted waveforms; at
higher masses these differences are much larger. The individual component
masses, which are very poorly determined with restricted waveforms, become
measurable with high accuracy if amplitude-corrected waveforms are used, with
errors as low as a few percent in Advanced LIGO and a few tenths of a percent
in EGO. The usual spin-orbit parameter is also poorly determined with
restricted waveforms (except for low-mass systems in EGO), but the full
waveforms give errors that are small compared to the largest possible value
consistent with the Kerr bound. This suggests a way of finding out if one or
both of the component objects violate this bound. We also briefly discuss the
effect of amplitude corrections on parameter estimation in Initial LIGO.Comment: 28 pages, many figures. Final version accepted by CQG. More in-depth
treatment of component mass errors and detectability of Kerr bound
violations; improved presentatio
Characterization of chaos in random maps
We discuss the characterization of chaotic behaviours in random maps both in
terms of the Lyapunov exponent and of the spectral properties of the
Perron-Frobenius operator. In particular, we study a logistic map where the
control parameter is extracted at random at each time step by considering
finite dimensional approximation of the Perron-Frobenius operatorComment: Plane TeX file, 15 pages, and 5 figures available under request to
[email protected]
System size resonance in coupled noisy systems and in the Ising model
We consider an ensemble of coupled nonlinear noisy oscillators demonstrating
in the thermodynamic limit an Ising-type transition. In the ordered phase and
for finite ensembles stochastic flips of the mean field are observed with the
rate depending on the ensemble size. When a small periodic force acts on the
ensemble, the linear response of the system has a maximum at a certain system
size, similar to the stochastic resonance phenomenon. We demonstrate this
effect of system size resonance for different types of noisy oscillators and
for different ensembles -- lattices with nearest neighbors coupling and
globally coupled populations. The Ising model is also shown to demonstrate the
system size resonance.Comment: 4 page
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