Binary black hole interactions provide potentially the strongest source of gravitational radiation for detectors currently under development. We present some results from the Binary Black Hole Grand Challenge Alliance three-dimensional Cauchy evolution module. These constitute essential steps towards modeling such interactions and predicting gravitational radiation waveforms. We report on single black hole evolutions and the first successful demonstration of a black hole moving freely through a three-dimensional computational grid via a Cauchy evolution: a hole moving ∼ 6M at 0.1c during a total evolution of duration ∼ 60M . The accurate computational modeling of black-hole interactions is essential to the confident detection of astrophysical gravitational radiation by future space-based detectors such as LISA and by the LIGO/VIRGO/GEO complex of ground-based detectors currently under construction. The sensitivity of these detectors will be significantly enhanced if accurate computer simulations of black-hole mergers can produce predictions of radiation waveforms [1]. The Binary Black Hole Grand Challenge Alliance [2] was funded in September 1993 to develop the computational infrastructure necessary accurately to simulate the coalescence of black-hole binaries. The primary objective of the resulting code will be the production of waveforms from binary black hole mergers. In this Letter we report on an important step towards achieving such simulations.A key difficulty in evolving black-hole spacetimes is handling the curvature singularity contained within each hole. The only viable means of accomplishing this over time scales required for binary coalescence appears to be black-hole excision: exclude all or part of the black-hole interior (and the singularity) from the computational domain and evolve only the exterior region [3,4
We present a method for extracting gravitational radiation from a three-dimensional numerical relativity simulation and, using the extracted data, to provide outer boundary conditions. The method treats dynamical gravitational variables as nonspherical perturbations of Schwarzschild geometry. We discuss a code which implements this method and present results of tests which have been performed with a three-dimensional numerical relativity code. [S0031-9007(98)05380-0] PACS numbers: 04.25. Dm, 04.30.Db, 04.70.Bw Numerical relativity represents the only currently viable method for obtaining solutions to Einstein equations for highly dynamical and strong field sources of gravitational radiation. Using these techniques to study coalescing black hole binaries is the purpose of the multi-institutional Binary Black Hole "Grand Challenge" Alliance effort [1] which is presently underway in the United States. This effort is also motivated by the prospect of observations with the next generation of gravitational wave detectors.In addition to tremendous demands on computational resources, implementing the standard 3 1 1 [2,3] formulation of Einstein theory as a Cauchy problem [4] is complicated considerably by the necessity of imposing boundary conditions which maintain numerical accuracy and the physical correctness of the solution. Both inner and outer boundary conditions have received considerable attention. Recent efforts on interior boundaries have focused on the excision of the interior of the black hole from the computational domain (see, for example, [5]). This paper will concentrate on the problem of outer boundary conditions applied at a finite radius around a source of gravitational waves.Proper boundary conditions on spacelike slices of asymptotically flat spacetimes are essential for the accurate computation of the gravitational wave forms produced in the strong field region that represent the observationally relevant aspect of the computation. Since it is not feasible to simulate on spacelike slices out to arbitrarily large distances from the source, it is necessary to extract gravitational waves comparatively near the strong field region and to have boundary conditions that allow radiation to pass cleanly off the mesh. If poor outgoing boundary conditions are imposed, spurious radiation is produced which can contaminate the computed gravitational wave form. Additionally, the outer boundary is usually close enough to the isolated source that backscatter of radiation from curvature is significant. This source of incoming radiation needs to be built into the outer boundary conditions. An approach to the extraction of gravitational wave information and the computation of outer boundary conditions that exploits the matching of the interior numerical solution with an exterior perturbative solution on spacelike slices has been developed during the past decade and applied to a number of different physical scenarios [6][7][8]. Extension of these techniques to three-dimensional (3D) simulations has been one of the ef...
We report new results which establish that the accurate three-dimensional numerical simulation of generic single-black-hole spacetimes has been achieved by characteristic evolution with unlimited long term stability. Our results include distorted, moving, and spinning single black holes, with evolution times up to 60 000M. [S0031-9007(98)
We use 47 gravitational wave sources from the Third LIGO–Virgo–Kamioka Gravitational Wave Detector Gravitational Wave Transient Catalog (GWTC–3) to estimate the Hubble parameter H(z), including its current value, the Hubble constant H 0. Each gravitational wave (GW) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and H(z). The source mass distribution displays a peak around 34 M ⊙, followed by a drop-off. Assuming this mass scale does not evolve with the redshift results in a H(z) measurement, yielding H 0 = 68 − 8 + 12 km s − 1 Mpc − 1 (68% credible interval) when combined with the H 0 measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the H 0 estimate from GWTC–1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event’s potential hosts. Assuming a fixed BBH population, we estimate a value of H 0 = 68 − 6 + 8 km s − 1 Mpc − 1 with the galaxy catalog method, an improvement of 42% with respect to our GWTC–1 result and 20% with respect to recent H 0 studies using GWTC–2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about H 0) is the well-localized event GW190814.
Strong cosmic censorship conjecture is central to the deterministic nature of general relativity, since it asserts that given any generic initial data on a spacelike hypersurface, the future can be uniquely predicted. However, recently it has been found that for charged black holes in asymptotically de Sitter spacetimes, the metric and massless scalar fields can be extended beyond the Cauchy horizon. This spells doom on the strong cosmic censorship conjecture, which prohibits precisely this scenario. In this work we try to understand the genericness of the above situation by studying the effect of NUT charge and conformally coupled scalar field on the violation of strong cosmic censorship conjecture for charged asymptotically de Sitter black holes. We have shown that even in the presence of the NUT charge and a conformally coupled scalar field strong cosmic censorship conjecture in indeed violated for such black holes with Cauchy horizon. Moreover, the presence of conformal coupling makes the situation even worse, in the sense that the scalar field is extendible across the Cauchy horizon as a C 1 function. On the other hand, the strong cosmic censorship conjecture is respected for conformally coupled scalar field in rotating black hole spacetimes with NUT charge. This reinforces the belief that possibly for astrophysical black holes, strong cosmic censorship conjecture is respected, irrespective of the nature of the scalar field.
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