Inspiraling black-hole binary spacetimes: Challenges in transitioning
  from analytical to numerical techniques
  We explore how a recently developed analytical black-hole binary spacetime
can be extended using numerical simulations to go beyond the slow-inspiral
phase. The analytic spacetime solves the Einstein field equations
approximately, with the approximation error becoming progressively smaller the
more separated the binary. To continue the spacetime beyond the slow-inspiral
phase, we need to transition. Such a transition was previously explored at
smaller separations. Here, we perform this transition at a separation of D=20M
(large enough that the analytical metric is expected to be accurate), and
evolve for six orbits. We find that small constraint violations can have large
dynamical effects, but these can be removed by using a constraint-damping
system like the conformal covariant formulation of the Z4 system. We find
agreement between the subsequent numerical spacetime and the predictions of
post-Newtonian theory for the waveform and inspiral rate that is within the
post-Newtonian truncation error.
