IMPROVED INITIAL DATA FOR BLACK-HOLE COLLISIONS

Numerical relativity codes now being developed will evolve initial dat a representing colliding black holes at a relatively late stage in the collision. The choice of initial data used for code development has b een made on the basis of mathematical definitiveness and usefulness fo r computational implementation. By using the ''particle limit'' (the l imit of an extreme ratio of masses of colliding holes) we recently sho wed that the standard choice is not a good representation of astrophys ically generated initial data. Here we show that, for the particle lim it, there is a very simple alternative choice that appears to give exc ellent results. That choice, ''convective'' initial data, is, roughly speaking, equivalent to the start of a time sequence of parametrized s olutions of the Hamiltonian constraint; for a particle in circular orb it, it is the initial data of the steady state solution on hypersurfac e. The implementation of related schemes for equal mass holes is discu ssed.