3,743 research outputs found
The optimal search for an astrophysical gravitational-wave background
Roughly every 2-10 minutes, a pair of stellar mass black holes merge
somewhere in the Universe. A small fraction of these mergers are detected as
individually resolvable gravitational-wave events by advanced detectors such as
LIGO and Virgo. The rest contribute to a stochastic background. We derive the
statistically optimal search strategy for a background of unresolved binaries.
Our method applies Bayesian parameter estimation to all available data. Using
Monte Carlo simulations, we demonstrate that the search is both "safe" and
effective: it is not fooled by instrumental artefacts such as glitches, and it
recovers simulated stochastic signals without bias. Given realistic
assumptions, we estimate that the search can detect the binary black hole
background with about one day of design sensitivity data versus
months using the traditional cross-correlation search. This framework
independently constrains the merger rate and black hole mass distribution,
breaking a degeneracy present in the cross-correlation approach. The search
provides a unified framework for population studies of compact binaries, which
is cast in terms of hyper-parameter estimation. We discuss a number of
extensions and generalizations including: application to other sources (such as
binary neutron stars and continuous-wave sources), simultaneous estimation of a
continuous Gaussian background, and applications to pulsar timing.Comment: 16 pages, 9 figure
Seedless clustering in all-sky searches for gravitational-wave transients
The problem of searching for unmodeled gravitational-wave bursts can be
thought of as a pattern recognition problem: how to find statistically
significant clusters in spectrograms of strain power when the precise signal
morphology is unknown. In a previous publication, we showed how "seedless
clustering" can be used to dramatically improve the sensitivity of searches for
long-lived gravitational-wave transients. In order to manage the computational
costs, this initial analysis focused on externally triggered searches where the
source location and emission time are both known to some degree of precision.
In this paper, we show how the principle of seedless clustering can be extended
to facilitate computationally-feasible, all-sky searches where the direction
and emission time of the source are entirely unknown. We further demonstrate
that it is possible to achieve a considerable reduction in computation time by
using graphical processor units (GPUs), thereby facilitating more sensitive
searches.Comment: 9 pages, 2 figure
Determining the population properties of spinning black holes
There are at least two formation scenarios consistent with the first
gravitational-wave observations of binary black hole mergers. In field models,
black hole binaries are formed from stellar binaries that may undergo common
envelope evolution. In dynamic models, black hole binaries are formed through
capture events in globular clusters. Both classes of models are subject to
significant theoretical uncertainties. Nonetheless, the conventional wisdom
holds that the distribution of spin orientations of dynamically merging black
holes is nearly isotropic while field-model black holes prefer to spin in
alignment with the orbital angular momentum. We present a framework in which
observations of black hole mergers can be used to measure ensemble properties
of black hole spin such as the typical black hole spin misalignment. We show
how to obtain constraints on population hyperparameters using minimal
assumptions so that the results are not strongly dependent on the uncertain
physics of formation models. These data-driven constraints will facilitate
tests of theoretical models and help determine the formation history of binary
black holes using information encoded in their observed spins. We demonstrate
that the ensemble properties of binary detections can be used to search for and
characterize the properties of two distinct populations of black hole mergers.Comment: 10 pages, 5 figures, 1 table. Minor revisions, published in PR
Detecting compact binary coalescences with seedless clustering
Compact binary coalescences are a promising source of gravitational waves for
second-generation interferometric gravitational-wave detectors. Although
matched filtering is the optimal search method for well-modeled systems,
alternative detection strategies can be used to guard against theoretical
errors (e.g., involving new physics and/or assumptions about spin/eccentricity)
while providing a measure of redundancy. In previous work, we showed how
"seedless clustering" can be used to detect long-lived gravitational-wave
transients in both targeted and all-sky searches. In this paper, we apply
seedless clustering to the problem of low-mass ()
compact binary coalescences for both spinning and eccentric systems. We show
that seedless clustering provides a robust and computationally efficient method
for detecting low-mass compact binaries
The mass distribution of Galactic double neutron stars
The conventional wisdom, dating back to 2012, is that the mass distribution
of Galactic double neutron stars is well-fit by a Gaussian distribution with a
mean of and a width of . With the recent discovery
of new Galactic double neutron stars and GW170817, the first neutron star
merger event to be observed with gravitational waves, it is timely to revisit
this model. In order to constrain the mass distribution of double neutron
stars, we perform Bayesian inference using a sample of 17 Galactic double
neutron stars effectively doubling the sample used in previous studies. We
expand the space of models so that the recycled neutron star need not be drawn
from the same distribution as the non-recycled companion. Moreover, we consider
different functional forms including uniform, single-Gaussian, and two-Gaussian
distributions. While there is insufficient data to draw firm conclusions, we
find positive support (a Bayes factor of 9) for the hypothesis that recycled
and non-recycled neutron stars have distinct mass distributions. The most
probable model---preferred with a Bayes factor of 29 over the conventional
model---is one in which the recycled neutron star mass is distributed according
to a two-Gaussian distribution and the non-recycled neutron star mass is
distributed uniformly. We show that precise component mass measurements of
double neutron stars are required in order to determine with high
confidence (a Bayes factor of 150) if recycled and non-recycled neutron stars
come from a common distribution. Approximately are needed in order to
establish the detailed shape of the distributions.Comment: Minor update of PSR J1913+1102 masses, 13 pages, 7 figures, 5 table
Evolution towards Smart Optical Networking: Where Artificial Intelligence (AI) meets the World of Photonics
Smart optical networks are the next evolution of programmable networking and
programmable automation of optical networks, with human-in-the-loop network
control and management. The paper discusses this evolution and the role of
Artificial Intelligence (AI)
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