4,485 research outputs found
The Final Merger of Black-Hole Binaries
Recent breakthroughs in the field of numerical relativity have led to
dramatic progress in understanding the predictions of General Relativity for
the dynamical interactions of two black holes in the regime of very strong
gravitational fields. Such black-hole binaries are important astrophysical
systems and are a key target of current and developing gravitational-wave
detectors. The waveform signature of strong gravitational radiation emitted as
the black holes fall together and merge provides a clear observable record of
the process. After decades of slow progress, these mergers and the
gravitational-wave signals they generate can now be routinely calculated using
the methods of numerical relativity. We review recent advances in understanding
the predicted physics of events and the consequent radiation, and discuss some
of the impacts this new knowledge is having in various areas of astrophysics.Comment: 57 pages; 9 figures. Updated references & fixed typos. Published
version is at
http://www.annualreviews.org/doi/abs/10.1146/annurev.nucl.010909.08324
Black-hole binaries, gravitational waves, and numerical relativity
Understanding the predictions of general relativity for the dynamical
interactions of two black holes has been a long-standing unsolved problem in
theoretical physics. Black-hole mergers are monumental astrophysical events,
releasing tremendous amounts of energy in the form of gravitational radiation,
and are key sources for both ground- and space-based gravitational-wave
detectors. The black-hole merger dynamics and the resulting gravitational
waveforms can only be calculated through numerical simulations of Einstein's
equations of general relativity. For many years, numerical relativists
attempting to model these mergers encountered a host of problems, causing their
codes to crash after just a fraction of a binary orbit could be simulated.
Recently, however, a series of dramatic advances in numerical relativity has
allowed stable, robust black-hole merger simulations. This remarkable progress
in the rapidly maturing field of numerical relativity, and the new
understanding of black-hole binary dynamics that is emerging is chronicled.
Important applications of these fundamental physics results to astrophysics, to
gravitational-wave astronomy, and in other areas are also discussed.Comment: 54 pages, 42 figures. Some typos corrected & references updated.
Essentially final published versio
Decoding mode-mixing in black-hole merger ringdown
Optimal extraction of information from gravitational-wave observations of
binary black-hole coalescences requires detailed knowledge of the waveforms.
Current approaches for representing waveform information are based on
spin-weighted spherical harmonic decomposition. Higher-order harmonic modes
carrying a few percent of the total power output near merger can supply
information critical to determining intrinsic and extrinsic parameters of the
binary. One obstacle to constructing a full multi-mode template of merger
waveforms is the apparently complicated behavior of some of these modes;
instead of settling down to a simple quasinormal frequency with decaying
amplitude, some modes show periodic bumps characteristic of
mode-mixing. We analyze the strongest of these modes -- the anomalous
harmonic mode -- measured in a set of binary black-hole merger waveform
simulations, and show that to leading order, they are due to a mismatch between
the spherical harmonic basis used for extraction in 3D numerical relativity
simulations, and the spheroidal harmonics adapted to the perturbation theory of
Kerr black holes. Other causes of mode-mixing arising from gauge ambiguities
and physical properties of the quasinormal ringdown modes are also considered
and found to be small for the waveforms studied here.Comment: 15 pages, 10 figures, 2 tables; new version has improved Figs. 1-3,
consistent labelling of simulations between Tables I & II,
additional/corrected references, and extra hyphen
Post-Newtonian Initial Data with Waves: Progress in Evolution
In Kelly et al. [Phys. Rev. D, 76:024008, 2007], we presented new binary
black-hole initial data adapted to puncture evolutions in numerical relativity.
This data satisfies the constraint equations to 2.5 post-Newtonian order, and
contains a transverse-traceless "wavy" metric contribution, violating the
standard assumption of conformal flatness. We report on progress in evolving
this data with a modern moving-puncture implementation of the BSSN equations in
several numerical codes. We discuss the effect of the new metric terms on junk
radiation and continuity of physical radiation extracted.Comment: 13 pages, 9 figures. Invited paper from Numerical Relativity and Data
Analysis (NRDA) 2009, Albert Einstein Institute, Potsdam. Corrected to match
published version
A Pentecost Ordination
Robert di Nardo: First Canadian Spiritan in 26 Year
I. Who Would Have Thought That Things Would Turn Out Like This!
The first of two talks given by Fr. Bernard Kelly in response to the question: How do we live our Spiritan spirituality so as to give \u27our\u27 special witness in today\u27s world, with reflection on the relevance (or otherwise) of our vocation to the youth of our time
II. Once Upon a Time
The second of two talks given by Fr. Bernard Kelly in response to the question: How do we live our Spiritan spirituality so as to give \u27our\u27 special witness in today\u27s world, with reflection on the relevance (or otherwise) of our vocation to the youth of our time
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