119231976
Intense electromagnetic outbursts from collapsing hypermassive neutron stars
We study the gravitational collapse of a magnetized neutron star using a novel numerical approach able to capture both the dynamics of the star and the behavior of the surrounding plasma. In this approach, a fully general relativistic magnetohydrodynamics implementation models the collapse of the star and provides appropriate boundary conditions to a force-free model which describes the stellar exterior. We validate this strategy by comparing with known results for the rotating monopole and aligned rotator solutions and then apply it to study both rotating and non-rotating stellar collapse scenarios, and contrast the behavior with what is obtained when employing the electrovacuum approximation outside the star. The non-rotating electrovacuum collapse is shown to agree qualitatively with a Newtonian model of the electromagnetic field outside a collapsing star. We illustrate and discuss a fundamental difference between the force-free and electrovacuum solutions, involving the appearance of large zones of electric-dominated field in the vacuum case. This provides a clear demonstration of how dissipative singularities appear generically in the non-linear time-evolution of force-free fluids. In both the rotating and non-rotating cases, our simulations indicate that the collapse induces a strong electromagnetic transient. In the case of sub-millisecond rotation, the magnetic field experiences strong winding and the transient carries much more energy. This result has important implications for models of gamma-ray bursts.
110973
Searching for gravitational waves from binary coalescence
We describe the implementation of a search for gravitational waves from compact binary coalescences in LIGO and Virgo data. This all-sky, all-time, multidetector search for binary coalescence has been used to search data taken in recent LIGO and Virgo runs. The search is built around a matched filter analysis of the data, augmented by numerous signal consistency tests designed to distinguish artifacts of non-Gaussian detector noise from potential detections. We demonstrate the search performance using Gaussian noise and data from the fifth LIGO science run and demonstrate that the signal consistency tests are capable of mitigating the effect of non-Gaussian noise and providing a sensitivity comparable to that achieved in Gaussian noise.
37135860
Efficiently enclosing the compact binary parameter space by singular-value decomposition
Gravitational-wave searches for the merger of compact binaries use matched filtering as the method of detecting signals and estimating parameters. Such searches construct a fine mesh of filters covering a signal parameter space at high density. Previously it has been shown that singular-value decomposition can reduce the effective number of filters required to search the data. Here we study how the basis provided by the singular-value decomposition changes dimension as a function of template-bank density. We will demonstrate that it is sufficient to use the basis provided by the singular-value decomposition of a low-density bank to accurately reconstruct arbitrary points within the boundaries of the template bank. Since this technique is purely numerical, it may have applications to interpolating the space of numerical relativity waveforms.
900545
Host Galaxies Catalog Used in LIGO Searches for Compact Binary Coalescence Events
An up-to-date catalog of nearby galaxies considered to be hosts of binary compact objects is provided, with complete information about sky position, distance, extinction-corrected blue luminosity, and error estimates. With our current understanding of binary evolution, rates of formation and coalescence for binary compact objects scale with massive-star formation, and hence the (extinction-corrected) blue luminosity of host galaxies. Coalescence events in binary compact objects are among the most promising gravitational-wave sources for ground-based gravitational-wave detectors such as LIGO. Our catalog and associated error estimates are important for the interpretation of analyses carried out for LIGO, in constraining the rates of compact binary coalescence, given an astrophysical population model for the sources considered. We discuss how the notion of effective distance, created to account for the antenna pattern of a gravitational-wave detector, must be used in conjunction with our catalog. We also note that the catalog provided can be used in other astronomical analysis of populations that scale with galaxy blue luminosity.
1751577
Improving the sensitivity of a search for coalescing binary black holes with nonprecessing spins in gravitational wave data
We demonstrate for the first time a search pipeline with improved sensitivity to gravitational waves from coalescing binary black holes with spins aligned to the orbital angular momentum by the inclusion of spin effects in the search templates. We study the pipeline recovery of simulated gravitational wave signals from aligned-spin binary black holes added to real detector noise, comparing the pipeline performance with aligned-spin filter templates to the same pipeline with nonspinning filter templates. Our results exploit a three-parameter phenomenological waveform family that models the full inspiral-merger-ringdown coalescence and treats the effect of aligned spins with a single effective spin parameter χ. We construct template banks from these waveforms by a stochastic placement method and use these banks as filters in the recently developed gstlal search pipeline. We measure the observable volume of the analysis pipeline for binary black hole signals with M_(total) and χ∈[0,0.85]. We find an increase in observable volume of up to 45% for systems with 0.2≤χ≤0.85 with almost no loss of sensitivity to signals with 0≤χ≤0.2. We also show that the use of spinning templates in the search pipeline provides for more accurate recovery of the binary mass parameters as well as an estimate of the effective spin parameter. We demonstrate this analysis on 25.9 days of data obtained from the Hanford and Livingston detectors in LIGO’s fifth observation run.
122800842
ANYONS AND SUPERCONDUCTIVITY: RANDOM PHASE APPROXIMATION
The two-dimensional ideal gas of particles obeying ν fractional statistics is recast as an interacting Fermi gas with long-range gauge potentials. A self-consistent dielectric description of the random phase approximation (RPA) provides a concise expression for the linear response of the fractional statistics gas to an external electromagnetic field. The RPA, believed to be correct for the present case of long-range interactions, yields two central results that are classic features of superconductivity: (1) a sharp undamped collective mode with a linear dispersion relation at long wavelengths: (2) a gauge-invariant Meissner effect in the transverse response to an external magnetic field.