377 research outputs found
Flux Limiter Methods in 3D Numerical Relativity
New numerical methods have been applied in relativity to obtain a numerical
evolution of Einstein equations much more robust and stable. Starting from 3+1
formalism and with the evolution equations written as a FOFCH (first-order flux
conservative hyperbolic) system, advanced numerical methods from CFD
(Computational Fluid Dynamics) have been successfully applied. A flux limiter
mechanism has been implemented in order to deal with steep gradients like the
ones usually associated with black hole spacetimes. As a test bed, the method
has been applied to 3D metrics describing propagation of nonlinear gauge waves.
Results are compared with the ones obtained with standard methods, showing a
great increase in both robustness and stability of the numerical algorithm.Comment: 9 pages, 5 figures. to be published in the Procedings of ERE0
Boosting jet power in black hole spacetimes
The extraction of rotational energy from a spinning black hole via the
Blandford-Znajek mechanism has long been understood as an important component
in models to explain energetic jets from compact astrophysical sources. Here we
show more generally that the kinetic energy of the black hole, both rotational
and translational, can be tapped, thereby producing even more luminous jets
powered by the interaction of the black hole with its surrounding plasma. We
study the resulting Poynting jet that arises from single boosted black holes
and binary black hole systems. In the latter case, we find that increasing the
orbital angular momenta of the system and/or the spins of the individual black
holes results in an enhanced Poynting flux.Comment: 7 pages, 5 figure
Orbital Dynamics of Binary Boson Star Systems
We extend our previous studies of head-on collisions of boson stars by
considering orbiting binary boson stars. We concentrate on equal mass binaries
and study the dynamical behavior of boson/boson and boson/antiboson pairs. We
examine the gravitational wave output of these binaries and compare with other
compact binaries. Such a comparison lets us probe the apparent simplicity
observed in gravitational waves produced by black hole binary systems. In our
system of interest however, there is an additional internal freedom which plays
a significant role in the system's dynamics, namely the phase of each star. Our
evolutions show rather simple behavior at early times, but large differences
occur at late times for the various initial configurations.Comment: 10 pages, 14 figure
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