556 research outputs found
Binary black hole merger dynamics and waveforms
We study dynamics and radiation generation in the last few orbits and merger
of a binary black hole system, applying recently developed techniques for
simulations of moving black holes. Our analysis of the gravitational radiation
waveforms and dynamical black hole trajectories produces a consistent picture
for a set of simulations with black holes beginning on circular-orbit
trajectories at a variety of initial separations. We find profound agreement at
the level of one percent among the simulations for the last orbit, merger and
ringdown. We are confident that this part of our waveform result accurately
represents the predictions from Einstein's General Relativity for the final
burst of gravitational radiation resulting from the merger of an astrophysical
system of equal-mass non-spinning black holes. The simulations result in a
final black hole with spin parameter a/m=0.69. We also find good agreement at a
level of roughly 10 percent for the radiation generated in the preceding few
orbits.Comment: 11 pages, 11 figures, submitted to PRD, update citations, minor
change
A Simple Procedure for Constructing 5'-Amino-Terminated Oligodeoxynucleotides in Aqueous Solution
A rapid method for the synthesis of oligodeoxynucleotides (ODNs) terminated by 5'-amino-5'-deoxythymidine is described. A 3'-phosphorylated ODN (the donor) is incubated in aqueous solution with 5'-amino- 5'-deoxythymidine in the presence of N-(3-dimethylaminopropyl)-)N'-ethylcarbodiimide hydrochloride (EDC), extending the donor by one residue via a phosphoramidate bond. Template- directed ligation of the extended donor and an acceptor ODN, followed by acid hydrolysis, yields the acceptor ODN extended by a single 5'-amino-5'-deoxythymidine residue at its 5'terminus
Beam Test of Silicon Strip Sensors for the ZEUS Micro Vertex Detector
For the HERA upgrade, the ZEUS experiment has designed and installed a high
precision Micro Vertex Detector (MVD) using single sided micro-strip sensors
with capacitive charge division. The sensors have a readout pitch of 120
microns, with five intermediate strips (20 micron strip pitch). An extensive
test program has been carried out at the DESY-II testbeam facility. In this
paper we describe the setup developed to test the ZEUS MVD sensors and the
results obtained on both irradiated and non-irradiated single sided micro-strip
detectors with rectangular and trapezoidal geometries. The performances of the
sensors coupled to the readout electronics (HELIX chip, version 2.2) have been
studied in detail, achieving a good description by a Monte Carlo simulation.
Measurements of the position resolution as a function of the angle of incidence
are presented, focusing in particular on the comparison between standard and
newly developed reconstruction algorithms.Comment: 41 pages, 21 figures, 2 tables, accepted for publication in NIM
Phenomenological template family for black-hole coalescence waveforms
Recent progress in numerical relativity has enabled us to model the
non-perturbative merger phase of the binary black-hole coalescence problem.
Based on these results, we propose a phenomenological family of waveforms which
can model the inspiral, merger, and ring-down stages of black hole coalescence.
We also construct a template bank using this family of waveforms and discuss
its implementation in the search for signatures of gravitational waves produced
by black-hole coalescences in the data of ground-based interferometers. This
template bank might enable us to extend the present inspiral searches to
higher-mass binary black-hole systems, i.e., systems with total mass greater
than about 80 solar masses, thereby increasing the reach of the current
generation of ground-based detectors.Comment: Minor changes, Submitted to Class. Quantum Grav. (Proc. GWDAW11
Simulation of Binary Black Hole Spacetimes with a Harmonic Evolution Scheme
A numerical solution scheme for the Einstein field equations based on
generalized harmonic coordinates is described, focusing on details not provided
before in the literature and that are of particular relevance to the binary
black hole problem. This includes demonstrations of the effectiveness of
constraint damping, and how the time slicing can be controlled through the use
of a source function evolution equation. In addition, some results from an
ongoing study of binary black hole coalescence, where the black holes are
formed via scalar field collapse, are shown. Scalar fields offer a convenient
route to exploring certain aspects of black hole interactions, and one
interesting, though tentative suggestion from this early study is that behavior
reminiscent of "zoom-whirl" orbits in particle trajectories is also present in
the merger of equal mass, non-spinning binaries, with appropriately fine-tuned
initial conditions.Comment: 16 pages, 14 figures; replaced with published versio
Binary black hole merger in the extreme mass ratio limit
We discuss the transition from quasi-circular inspiral to plunge of a system
of two nonrotating black holes of masses and in the extreme mass
ratio limit . In the spirit of the Effective One Body
(EOB) approach to the general relativistic dynamics of binary systems, the
dynamics of the two black hole system is represented in terms of an effective
particle of mass moving in a (quasi-)Schwarzschild
background of mass and submitted to an
radiation reaction force defined by Pad\'e resumming high-order Post-Newtonian
results. We then complete this approach by numerically computing, \`a la
Regge-Wheeler-Zerilli, the gravitational radiation emitted by such a particle.
Several tests of the numerical procedure are presented. We focus on
gravitational waveforms and the related energy and angular momentum losses. We
view this work as a contribution to the matching between analytical and
numerical methods within an EOB-type framework.Comment: 14 pages, six figures. Revised version. To appear in the CQG special
issue based around New Frontiers in Numerical Relativity conference, Golm
(Germany), July 17-21 200
Are moving punctures equivalent to moving black holes?
When simulating the inspiral and coalescence of a binary black-hole system,
special care needs to be taken in handling the singularities. Two main
techniques are used in numerical-relativity simulations: A first and more
traditional one ``excises'' a spatial neighbourhood of the singularity from the
numerical grid on each spacelike hypersurface. A second and more recent one,
instead, begins with a ``puncture'' solution and then evolves the full
3-metric, including the singular point. In the continuum limit, excision is
justified by the light-cone structure of the Einstein equations and, in
practice, can give accurate numerical solutions when suitable discretizations
are used. However, because the field variables are non-differentiable at the
puncture, there is no proof that the moving-punctures technique is correct,
particularly in the discrete case. To investigate this question we use both
techniques to evolve a binary system of equal-mass non-spinning black holes. We
compare the evolution of two curvature 4-scalars with proper time along the
invariantly-defined worldline midway between the two black holes, using
Richardson extrapolation to reduce the influence of finite-difference
truncation errors. We find that the excision and moving-punctures evolutions
produce the same invariants along that worldline, and thus the same spacetimes
throughout that worldline's causal past. This provides convincing evidence that
moving-punctures are indeed equivalent to moving black holes.Comment: 4 pages, 3 eps color figures; v2 = major revisions to introduction &
conclusions based on referee comments, but no change in analysis or result
Gauge conditions for long-term numerical black hole evolutions without excision
Numerical relativity has faced the problem that standard 3+1 simulations of
black hole spacetimes without singularity excision and with singularity
avoiding lapse and vanishing shift fail after an evolution time of around
30-40M due to the so-called slice stretching. We discuss lapse and shift
conditions for the non-excision case that effectively cure slice stretching and
allow run times of 1000M and more.Comment: 19 pages, 14 figures, REVTeX, Added a missing Acknowledgmen
Towards absorbing outer boundaries in General Relativity
We construct exact solutions to the Bianchi equations on a flat spacetime
background. When the constraints are satisfied, these solutions represent in-
and outgoing linearized gravitational radiation. We then consider the Bianchi
equations on a subset of flat spacetime of the form [0,T] x B_R, where B_R is a
ball of radius R, and analyze different kinds of boundary conditions on
\partial B_R. Our main results are: i) We give an explicit analytic example
showing that boundary conditions obtained from freezing the incoming
characteristic fields to their initial values are not compatible with the
constraints. ii) With the help of the exact solutions constructed, we determine
the amount of artificial reflection of gravitational radiation from
constraint-preserving boundary conditions which freeze the Weyl scalar Psi_0 to
its initial value. For monochromatic radiation with wave number k and arbitrary
angular momentum number l >= 2, the amount of reflection decays as 1/(kR)^4 for
large kR. iii) For each L >= 2, we construct new local constraint-preserving
boundary conditions which perfectly absorb linearized radiation with l <= L.
(iv) We generalize our analysis to a weakly curved background of mass M, and
compute first order corrections in M/R to the reflection coefficients for
quadrupolar odd-parity radiation. For our new boundary condition with L=2, the
reflection coefficient is smaller than the one for the freezing Psi_0 boundary
condition by a factor of M/R for kR > 1.04. Implications of these results for
numerical simulations of binary black holes on finite domains are discussed.Comment: minor revisions, 30 pages, 6 figure
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