Post-Newtonian Quasicircular Initial Orbits for Numerical Relativity
  We use post-Newtonian (PN) approximations to determine the initial orbital
and spin parameters of black hole binaries that lead to low-eccentricity
inspirals when evolved with numerical relativity techniques. In particular, we
seek initial configurations that lead to very small eccentricities at small
separations, as is expected for astrophysical systems. We consider three cases:
(i) quasicircular orbits with no radial velocity, (ii) quasicircular orbits
with an initial radial velocity determined by radiation reaction, and (iii)
parameters obtained form evolution of the PN equations of motion from much
larger separations. We study seven cases of spinning, nonprecessing, unequal
mass binaries. We then use several definitions of the eccentricity, based on
orbital separations and waveform phase and amplitude, and find that using the
complete 3PN Hamiltonian for quasicircular orbits to obtain the tangential
orbital momentum, and using the highest-known-order radiation reaction
expressions to obtain the radial momentum, leads to the lowest eccentricity.
The accuracy of this method even exceeds that of inspiral data based on 3PN and
4PN evolutions.
