*Black Hole-Black Hole Binary Merger Simulations in Full General
Relativity*

** Zachariah B.
Etienne
Yuk Tung Liu
Stuart L.
Shapiro
Thomas W. Baumgarte**

**ABSTRACT**

The calculation of a binary black hole inspiral and
coalescence is one of the great triumphs of numerical relativity. The
successful solution to this problem has required contributions from many
people working over many years. The chief ingredients include a stable
algorithm to solve Einstein's field equations in 3+1 dimensions, valid
initial data for two black holes in quasiequilibrium circular orbit, a
means of avoiding the black hole spacetime singularity on the
computational grid, a good gauge choice for performing the evolution,
and adaptivity to achieve high resolution both in the strong-field
region near the black holes and in the far zone where the gravitational
waves are measured. By now, solving binary black hole coalescence on
computers has become almost routine.

By simulating the gravitational radiation waveforms from black
hole-black hole (BHBH) mergers, we hope to test strong-field general
relativity by comparing theoretical waveform templates with measurements
made by ground-based laser interferometers like LIGO (Laser
Inteferometer Gravitational Wave Observatory), VIRGO, GEO, and TAMA, and
space-based interferometers like LISA (Laser Interferometer Space
Antenna). These numerical calculations are especially important because
BHBH binaries are expected to be among the most promising sources of
gravitational waves. Also, BHBH merger calculations serve as a warm-up
for the calculations of binary black hole-neutron star (BHNS) mergers.
BHNS merger calculations are more challenging because of the presence of
hydrodynamic matter.

The representative BHBH calculation summarized here was performed with the
Illinois relativistic hydrodynamics code with the hydrodynamics turned
"off" to solve the pure vacuum problem. The code utilizes the BSSN
scheme for evolving the Einstein equations and employs AMR (adaptive
mesh refinement). The initial data is "puncture" data for a BHBH binary
in a quasicircular orbit and the evolution is performed with "moving
puncture" gauge conditions.

*Scientific visualization by*

last updated 17 Sept 09 by TC