4,113 research outputs found
Applying black hole perturbation theory to numerically generated spacetimes
Nonspherical perturbation theory has been necessary to understand the meaning
of radiation in spacetimes generated through fully nonlinear numerical
relativity. Recently, perturbation techniques have been found to be successful
for the time evolution of initial data found by nonlinear methods. Anticipating
that such an approach will prove useful in a variety of problems, we give here
both the practical steps, and a discussion of the underlying theory, for taking
numerically generated data on an initial hypersurface as initial value data and
extracting data that can be considered to be nonspherical perturbations.Comment: 14 pages, revtex3.0, 5 figure
Cauchy-perturbative matching and outer boundary conditions I: Methods and tests
We present a new method of extracting gravitational radiation from
three-dimensional numerical relativity codes and providing outer boundary
conditions. Our approach matches the solution of a Cauchy evolution of
Einstein's equations to a set of one-dimensional linear wave equations on a
curved background. We illustrate the mathematical properties of our approach
and discuss a numerical module we have constructed for this purpose. This
module implements the perturbative matching approach in connection with a
generic three-dimensional numerical relativity simulation. Tests of its
accuracy and second-order convergence are presented with analytic linear wave
data.Comment: 13 pages, 6 figures, RevTe
Cauchy-perturbative matching and outer boundary conditions: computational studies
We present results from a new technique which allows extraction of
gravitational radiation information from a generic three-dimensional numerical
relativity code and provides stable outer boundary conditions. In our approach
we match the solution of a Cauchy evolution of the nonlinear Einstein field
equations to a set of one-dimensional linear equations obtained through
perturbation techniques over a curved background. We discuss the validity of
this approach in the case of linear and mildly nonlinear gravitational waves
and show how a numerical module developed for this purpose is able to provide
an accurate and numerically convergent description of the gravitational wave
propagation and a stable numerical evolution.Comment: 20 pages, RevTe
The collision of boosted black holes
We study the radiation from a collision of black holes with equal and
opposite linear momenta. Results are presented from a full numerical relativity
treatment and are compared with the results from a ``close-slow''
approximation. The agreement is remarkable, and suggests several insights about
the generation of gravitational radiation in black hole collisions.Comment: 8 pages, RevTeX, 3 figures included with eps
Waveform propagation in black hole spacetimes: evaluating the quality of numerical solutions
We compute the propagation and scattering of linear gravitational waves off a
Schwarzschild black hole using a numerical code which solves a generalization
of the Zerilli equation to a three dimensional cartesian coordinate system.
Since the solution to this problem is well understood it represents a very good
testbed for evaluating our ability to perform three dimensional computations of
gravitational waves in spacetimes in which a black hole event horizon is
present.Comment: 13 pages, RevTeX, to appear in Phys. Rev.
Drag resistance of 2D electronic microemulsions
Motivated by recent experiments of Pillarisetty {\it et al}, \prl {\bf 90},
226801 (2003), we present a theory of drag in electronic double layers at low
electron concentration. We show that the drag effect in such systems is
anomolously large, it has unusual temperature and magnetic field dependences
accociated with the Pomeranchuk effect, and does not vanish at zero
temperature
Comment on "Zeeman-Driven Lifshitz Transition: A Model for the Experimentally Observed Fermi-Surface Reconstruction in YbRh2Si2"
In Phys. Rev. Lett. 106, 137002 (2011), A. Hackl and M. Vojta have proposed
to explain the quantum critical behavior of YbRh2Si2 in terms of a
Zeeman-induced Lifshitz transition of an electronic band whose width is about 6
orders of magnitude smaller than that of conventional metals. Here, we note
that the ultra-narrowness of the proposed band, as well as the proposed
scenario per se, lead to properties which are qualitatively inconsistent with
the salient features observed in YbRh2Si2 near its quantum critical point.Comment: 3 page
Gravitational wave extraction and outer boundary conditions by perturbative matching
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
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