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The Einstein Toolkit: A Community Computational Infrastructure for Relativistic Astrophysics
, 2011
"... Abstract. We describe the Einstein Toolkit, a communitydriven, freely accessible computational infrastructure intended for use in numerical relativity, relativistic astrophysics, and other applications. The Toolkit, developed by a collaboration involving researchers from multiple institutions aroun ..."
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Abstract. We describe the Einstein Toolkit, a communitydriven, freely accessible computational infrastructure intended for use in numerical relativity, relativistic astrophysics, and other applications. The Toolkit, developed by a collaboration involving researchers from multiple institutions around the world, combines a core set of components needed to simulate astrophysical objects such as black holes, compact objects, and collapsing stars, as well as a full suite of analysis tools. The Einstein Toolkit is currently based on the Cactus Framework for highperformance computing and the Carpet adaptive mesh refinement driver. It implements spacetime evolution via the BSSN evolution system and generalrelativistic hydrodynamics in a finitevolume discretization. The toolkit is under continuous development and contains many new code components that have been publicly released for the first time and are described in this article. We discuss the motivation behind the release of the toolkit, the philosophy underlying its development, and the goals of the project. A summary of the implemented numerical techniques is included, as are results of numerical test covering a variety of sample astrophysical problems.
Heavy ions and string theory
"... We review a selection of recent developments in the application of ideas of string theory to heavy ion physics. Our topics divide naturally into equilibrium and nonequilibrium phenomena. On the nonequilibrium side, we discuss generalizations of Bjorken flow, numerical simulations of black hole fo ..."
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We review a selection of recent developments in the application of ideas of string theory to heavy ion physics. Our topics divide naturally into equilibrium and nonequilibrium phenomena. On the nonequilibrium side, we discuss generalizations of Bjorken flow, numerical simulations of black hole formation in asymptotically antide Sitter geometries, equilibration in the dual field theory, and hard probes. On the equilibrium side, we summarize improved holographic QCD, extraction of transport coefficients, inclusion of chemical potentials, and approaches to the phase diagram. We close with some possible directions for future research. 1 ar
Continuum and Discrete InitialBoundaryValue Problems and Einstein’s Field Equations
, 2012
"... Many evolution problems in physics are described by partial differential equations on an infinite domain; therefore, one is interested in the solutions to such problems for a given initial dataset. A prominent example is the binary black hole problem within Einstein’s theory of gravitation, in which ..."
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Many evolution problems in physics are described by partial differential equations on an infinite domain; therefore, one is interested in the solutions to such problems for a given initial dataset. A prominent example is the binary black hole problem within Einstein’s theory of gravitation, in which one computes the gravitational radiation emitted from the inspiral of the two black holes, merger and ringdown. Powerful mathematical tools can be used to establish qualitative statements about the solutions, such as their existence, uniqueness, continuous dependence on the initial data, or their asymptotic behavior over large time scales. However, one is often interested in computing the solution itself, and unless the partial differential equation is very simple, or the initial data possesses a high degree of symmetry, this computation requires approximation by numerical discretization. When solving such discrete problems on a machine, one is faced with a finite limit to computational resources, which leads to the replacement of the infinite continuum domain with a finite computer grid. This, in turn, leads to a discrete initialboundary value problem. The hope is to recover, with high accuracy, the exact solution in the limit where the grid spacing converges to zero with the boundary being
INSPIRALMERGERRINGDOWN MODELS FOR SPINNING BLACKHOLE BINARIES AT THE INTERFACE BETWEEN ANALYTICAL AND NUMERICAL RELATIVITY
"... The longsought direct detection of gravitational waves may only be a few years away, as a new generation of interferometric experiments of unprecedented sensitivity will start operating in 2015. These experiments will look for gravitational waves with frequencies from 10 to about 1000 Hz, thus tar ..."
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The longsought direct detection of gravitational waves may only be a few years away, as a new generation of interferometric experiments of unprecedented sensitivity will start operating in 2015. These experiments will look for gravitational waves with frequencies from 10 to about 1000 Hz, thus targeting astrophysical sources such as coalescing binaries of compact objects, core collapse supernovae, and spinning neutron stars, among others. The search strategy for gravitational waves emitted by compactobject binaries consists in filtering the output of the detectors with template waveforms that describe plausible signals, as predicted by general relativity, in order to increase the signaltonoise ratio. In this work, we modeled these systems through the effectiveonebody approach to the generalrelativistic 2body problem. This formalism rests on the idea that binary coalescence is universal across different mass ratios, from the testparticle limit to the equalmass regime. It bridges the gap between postNewtonian theory (valid in the slowmotion, weakfield limit) and blackhole perturbation theory (valid in the small massratio limit, but not limited to slow motion). The
2.5PN kick from blackhole binaries in circular orbit: Nonspinning case
"... Abstract. Using the Multipolar postMinskowskian formalism, we compute the linear momentum flux from blackhole binaries in circular orbits and having no spins. The total linear momentum flux contains various types of instantaneous (which are functions of the retarded time) and hereditary (which de ..."
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Abstract. Using the Multipolar postMinskowskian formalism, we compute the linear momentum flux from blackhole binaries in circular orbits and having no spins. The total linear momentum flux contains various types of instantaneous (which are functions of the retarded time) and hereditary (which depends on the dynamics of the binary in the past) terms both of which are analytically computed. In addition to the inspiral contribution, we use a simple model of plunge to compute the kick or recoil accumulated during this phase. 1.
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"... Noname manuscript No. (will be inserted by the editor) Massive binary black holes in galactic nuclei and their path to coalescence ..."
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Noname manuscript No. (will be inserted by the editor) Massive binary black holes in galactic nuclei and their path to coalescence
Three little pieces for computer and relativity
"... Abstract. Numerical relativity has made big strides over the last decade. A number of problems that have plagued the field for years have now been mostly solved. This progress has transformed numerical relativity into a powerful tool to explore fundamental problems in physics and astrophysics, and I ..."
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Abstract. Numerical relativity has made big strides over the last decade. A number of problems that have plagued the field for years have now been mostly solved. This progress has transformed numerical relativity into a powerful tool to explore fundamental problems in physics and astrophysics, and I present here three representative examples. These “three little pieces ” reflect a personal choice and describe work that I am particularly familiar with. However, many more examples could be made. 1.
Noname manuscript No. (will be inserted by the editor) Twostep
"... greedy algorithm for reduced order quadratures ..."
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