48 research outputs found
Matched Filtering of Numerical Relativity Templates of Spinning Binary Black Holes
Tremendous progress has been made towards the solution of the
binary-black-hole problem in numerical relativity. The waveforms produced by
numerical relativity will play a role in gravitational wave detection as either
test-beds for analytic template banks or as template banks themselves. As the
parameter space explored by numerical relativity expands, the importance of
quantifying the effect that each parameter has on first the detection of
gravitational waves and then the parameter estimation of their sources
increases. In light of this, we present a study of equal-mass, spinning
binary-black-hole evolutions through matched filtering techniques commonly used
in data analysis. We study how the match between two numerical waveforms varies
with numerical resolution, initial angular momentum of the black holes and the
inclination angle between the source and the detector. This study is limited by
the fact that the spinning black-hole-binaries are oriented axially and the
waveforms only contain approximately two and a half orbits before merger. We
find that for detection purposes, spinning black holes require the inclusion of
the higher harmonics in addition to the dominant mode, a condition that becomes
more important as the black-hole-spins increase. In addition, we conduct a
preliminary investigation of how well a template of fixed spin and inclination
angle can detect target templates of arbitrary spin and inclination for the
axial case considered here
Robustness of Binary Black Hole Mergers in the Presence of Spurious Radiation
We present an investigation into how sensitive the last orbits and merger of
binary black hole systems are to the presence of spurious radiation in the
initial data. Our numerical experiments consist of a binary black hole system
starting the last couple of orbits before merger with additional spurious
radiation centered at the origin and fixed initial angular momentum. As the
energy in the added spurious radiation increases, the binary is invariably
hardened for the cases we tested, i.e. the merger of the two black holes is
hastened. The change in merger time becomes significant when the additional
energy provided by the spurious radiation increases the Arnowitt-Deser-Misner
(ADM) mass of the spacetime by about 1%. While the final masses of the black
holes increase due to partial absorption of the radiation, the final spins
remain constant to within our numerical accuracy. We conjecture that the
spurious radiation is primarily increasing the eccentricity of the orbit and
secondarily increasing the mass of the black holes while propagating out to
infinity.Comment: 12 pages, 12 figure
Existence, Uniqueness and Regularity for Solutions of the Conical Diffraction Problem
This paper is devoted to the analysis of two Helmholtz equations in ℝ2 coupled via quasiperiodic transmission conditions on a set of piecewise smooth interfaces. The solution of this system is quasi-periodic in one direction and satisfies outgoing wave conditions with respect to the other direction. It is shown that Maxwell's equations for the diffraction of a time-harmonic oblique incident plane wave by periodic interfaces can be reduced to problems of this kind. The analysis is based on a strongly elliptic variational formulation of the differential problem in a bounded periodic cell involving nonlocal boundary operators. We obtain existence and uniqueness results for solutions corresponding to electromagnetic fields with locally finite energy. Special attention is paid to the regularity and leading asymptotics of solutions near the edges of the interface
Probing the Binary Black Hole Merger Regime with Scalar Perturbations
We present results obtained by scattering a scalar field off the curved
background of a coalescing binary black hole system. A massless scalar field is
evolved on a set of fixed backgrounds, each provided by a spatial hypersurface
generated numerically during a binary black hole merger. We show that the
scalar field scattered from the merger region exhibits quasinormal ringing once
a common apparent horizon surrounds the two black holes. This occurs earlier
than the onset of the perturbative regime as measured by the start of the
quasinormal ringing in the gravitational waveforms. We also use the scalar
quasinormal frequencies to associate a mass and a spin with each hypersurface,
and observe the compatibility of this measure with the horizon mass and spin
computed from the dynamical horizon framework.Comment: 10 Pages and 6 figure
From Physics Model to Results: An Optimizing Framework for Cross-Architecture Code Generation
Starting from a high-level problem description in terms of partial
differential equations using abstract tensor notation, the Chemora framework
discretizes, optimizes, and generates complete high performance codes for a
wide range of compute architectures. Chemora extends the capabilities of
Cactus, facilitating the usage of large-scale CPU/GPU systems in an efficient
manner for complex applications, without low-level code tuning. Chemora
achieves parallelism through MPI and multi-threading, combining OpenMP and
CUDA. Optimizations include high-level code transformations, efficient loop
traversal strategies, dynamically selected data and instruction cache usage
strategies, and JIT compilation of GPU code tailored to the problem
characteristics. The discretization is based on higher-order finite differences
on multi-block domains. Chemora's capabilities are demonstrated by simulations
of black hole collisions. This problem provides an acid test of the framework,
as the Einstein equations contain hundreds of variables and thousands of terms.Comment: 18 pages, 4 figures, accepted for publication in Scientific
Programmin
Binary Black Holes: Spin Dynamics and Gravitational Recoil
We present a study of spinning black hole binaries focusing on the spin
dynamics of the individual black holes as well as on the gravitational recoil
acquired by the black hole produced by the merger. We consider two series of
initial spin orientations away from the binary orbital plane. In one of the
series, the spins are anti-aligned; for the second series, one of the spins
points away from the binary along the line separating the black holes. We find
a remarkable agreement between the spin dynamics predicted at 2nd
post-Newtonian order and those from numerical relativity. For each
configuration, we compute the kick of the final black hole. We use the kick
estimates from the series with anti-aligned spins to fit the parameters in the
\KKF{,} and verify that the recoil along the direction of the orbital angular
momentum is and on the orbital plane ,
with the angle between the spin directions and the orbital angular
momentum. We also find that the black hole spins can be well estimated by
evaluating the isolated horizon spin on spheres of constant coordinate radius.Comment: 15 pages, 10 figures, replaced with version accepted for publication
in PR
Gravitational recoil from spinning binary black hole mergers
The inspiral and merger of binary black holes will likely involve black holes
with both unequal masses and arbitrary spins. The gravitational radiation
emitted by these binaries will carry angular as well as linear momentum. A net
flux of emitted linear momentum implies that the black hole produced by the
merger will experience a recoil or kick. Previous studies have focused on the
recoil velocity from unequal mass, non-spinning binaries. We present results
from simulations of equal mass but spinning black hole binaries and show how a
significant gravitational recoil can also be obtained in these situations. We
consider the case of black holes with opposite spins of magnitude
aligned/anti-aligned with the orbital angular momentum, with the
dimensionless spin parameters of the individual holes. For the initial setups
under consideration, we find a recoil velocity of V = 475 \KMS a.
Supermassive black hole mergers producing kicks of this magnitude could result
in the ejection from the cores of dwarf galaxies of the final hole produced by
the collision.Comment: 8 pages, 8 figures, replaced with version accepted for publication in
Ap
Superkicks in Hyperbolic Encounters of Binary Black Holes
Generic inspirals and mergers of binary black holes produce beamed emission
of gravitational radiation that can lead to a gravitational recoil or kick of
the final black hole. The kick velocity depends on the mass ratio and spins of
the binary as well as on the dynamics of the binary configuration. Studies have
focused so far on the most astrophysically relevant configuration of
quasi-circular inspirals, for which kicks as large as 3,300 km/s have been
found. We present the first study of gravitational recoil in hyperbolic
encounters. Contrary to quasi-circular configurations, in which the beamed
radiation tends to average during the inspiral, radiation from hyperbolic
encounters is plunge dominated, resulting in an enhancement of preferential
beaming. As a consequence, it is possible to achieve kick velocities as large
as 10,000 km/s.Comment: 4 pages, 5 figures, 1 tabl
Unequal Mass Binary Black Hole Plunges and Gravitational Recoil
We present results from fully nonlinear simulations of unequal mass binary
black holes plunging from close separations well inside the innermost stable
circular orbit with mass ratios q = M_1/M_2 = {1,0.85,0.78,0.55,0.32}, or
equivalently, with reduced mass parameters . For each case, the initial binary orbital
parameters are chosen from the Cook-Baumgarte equal-mass ISCO configuration. We
show waveforms of the dominant l=2,3 modes and compute estimates of energy and
angular momentum radiated. For the plunges from the close separations
considered, we measure kick velocities from gravitational radiation recoil in
the range 25-82 km/s. Due to the initial close separations our kick velocity
estimates should be understood as a lower bound. The close configurations
considered are also likely to contain significant eccentricities influencing
the recoil velocity.Comment: 12 pages, 5 figures, to appear in "New Frontiers" special issue of
CQ