HEAD-ON COLLISION OF 2 BLACK-HOLES - COMPARISON OF DIFFERENT APPROACHES

A benchmark problem for numerical relativity has been the head-on Coll ision of two black holes starting from the ''Misner initial data,'' a closed form momentarily stationary solution to the con- :: straint equ ations with an adjustable closeness parameter mu(0). We show here how an eclectic mixture of approximation methods can provide both an effic ient means of determining the time development of the initial data and a good understanding of the physics of the problem. When the Misner d ata, are chosen to correspond to holes initially very close together, a common horizon surrounds both holes and the geometry exterior to the horizon can be treated as a nonspherical perturbation of a single Sch warzschild hole. When the holes are initially well separated the probl em can be treated with a different approximation scheme, ''the particl e-membrane method.'' For all initial separations, numerical relativity is in principle applicable, but is costly and of uncertain accuracy. We present here a comparison of the different approaches. We compare w aveform, for l = 2 and l = 4 radiation, for different values of mu(0), from the three different approaches to the problem.