Spin flips in generic black hole binaries
  We study the spin dynamics of individual black holes in a binary system. In
particular we focus on the polar precession of spins and the possibility of a
complete flip of spins with respect to the orbital plane. We perform a full
numerical simulation that displays these characteristics. We evolve equal mass
binary spinning black holes for $t=20,000M$ from an initial proper separation
of $d=25M$ down to merger after 48.5 orbits. We compute the gravitational
radiation from this system and compare it to 3.5 post-Newtonian generated
waveforms finding close agreement. We then further use 3.5 post-Newtonian
evolutions to show the extension of this spin {flip-flop} phenomenon to unequal
mass binaries. We also provide analytic expressions to approximate the maximum
{flip-flop} angle and frequency in terms of the binary spins and mass ratio
parameters at a given orbital radius. Finally we discuss the effect this spin
{flip-flop} would have on accreting matter and other potential observational
effects.
