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L. Rezzolla

Publications and source records attributed to L. Rezzolla.

46 records · Page 3Linked to original sources
arXiv1999

Constructing a Mass-Current Radiation-Reaction Force For Numerical Simulations

We present a new set of 3.5 Post-Newtonian equations in which Newtonian hydrodynamics is coupled to the nonconservative effects of gravitational radiation emission. Our formalism differs in two significant ways from a similar 3.5 Post-Newtonian approach proposed by Blanchet (1993, 1997). Firstly we concentrate only on the radiation-reaction effects produced by a time-varying mass-current quadrupole $S_{ij}$. Secondly, we adopt a gauge in which the radiation-reaction force densities depend on the fourth time derivative of $S_{ij}$, rather than on the fifth, as in Blanchet's approach. This difference makes our formalism particularly well-suited to numerical implementation and could prove useful in performing fully numerical simulations of the recently discovered $r$-mode instability for rotating neutron stars subject to axial perturbations.

gr-qc↗
arXiv1998

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.

gr-qc↗
arXiv1997

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.

gr-qc↗
arXiv1997

Boosted three-dimensional black-hole evolutions with singularity excision

Binary black hole interactions provide potentially the strongest source of gravitational radiation for detectors currently under development. We present some results from the Binary Black Hole Grand Challenge Alliance three- dimensional Cauchy evolution module. These constitute essential steps towards modeling such interactions and predicting gravitational radiation waveforms. We report on single black hole evolutions and the first successful demonstration of a black hole moving freely through a three-dimensional computational grid via a Cauchy evolution: a hole moving ~6M at 0.1c during a total evolution of duration ~60M.

gr-qc↗
arXiv1997

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.

gr-qc↗
arXiv1996

Baryon number segregation at the end of the cosmological quark-hadron transition

One of the most interesting questions regarding a possible first order cosmological quark--hadron phase transition concerns the final fate of the baryon number contained within the disconnected quark regions at the end of the transition. We here present a detailed investigation of the hydrodynamical evolution of an evaporating quark drop, using a multi-component fluid description to follow the mechanisms of baryon number segregation. With this approach, we are able to take account of the simultaneous effects of baryon number flux suppression at the phase interface, entropy extraction by means of particles having long mean-free-paths, and baryon number diffusion. A range of computations has been performed to investigate the permitted parameter-space and this has shown that significant baryon number concentrations, perhaps even up to densities above that of nuclear matter, represent an inevitable outcome within this scenario.

hep-ph↗
arXiv1995

Evaporation of cosmological quark drops and relativistic radiative transfer

We discuss the results of a full relativistic treatment of the hydrodynamics of disconnected quark regions during the final stages of the cosmological quark-hadron transition. In this study, which represents a further development of a previous analysis of the evaporation of cosmological quark drops, the effects of long range energy and momentum transfer via electromagnetically interacting particles are consistently taken into account. For this purpose, a set of relativistic Lagrangian equations describing the evolution of the strongly interacting fluids is coupled to a system of equivalent equations accounting for the hydrodynamics of the fluid of electromagnetically interacting particles. The complete set of equations has then been solved numerically and results are presented from this. The inclusion of relativistic radiative transfer produces significantly different results, with the formation of high density regions at the end of the drop evaporation being particularly relevant. A comparison is made with results obtained for the previous radiation-free model and the cosmological implications concerning baryon number concentrations are briefly discussed.

astro-ph↗
arXiv1995

EVAPORATION OF QUARK DROPS DURING THE COSMOLOGICAL Q-H TRANSITION

We have carried out a study of the hydrodynamics of disconnected quark regions during the final stages of the cosmological quark-hadron transition. A set of relativistic Lagrangian equations is presented for following the evaporation of a single quark drop and results from the numerical solution of this are discussed. A self-similar solution is shown to exist and the formation of baryon number density inhomogeneities at the end of the drop contraction is discussed.

astro-ph↗
arXiv1994

Hydrodynamics of the Cosmological Quark-Hadron Transition in the Presence of Long-Range Energy and Momentum Transfer

Two previous papers in this series have presented a study of the growth of hadronic bubbles during the cosmological Quark--Hadron transition, treating the material within each phase as a single perfect fluid. Here, we extend the analysis to include the effects of long-range energy and momentum transfer by weakly and electromagnetically interacting particles. After a short review of the formalism adopted, we discuss the numerical strategies used in the computer code which has been constructed in order to solve this system of equations. Results for the growth of single hadronic bubbles are also presented.

astro-ph↗