INITIAL DATA FOR SUPERPOSED ROTATING BLACK-HOLES - ART. NO. 104003

The standard approach to initial data for both analytic an numerical c omputations of black hole collisions has been to use a conformally fla t initial geometry. Among other advantages, this choice allows the sim ple superposition of holes with arbitrary mass, location and spin. The conformally flat restriction, however, is inappropriate to the study of Kerr holes, for which the standard constant-time slice is not confo rmally Rat. Here we point out that for axisymmetric arrangements of ro tating holes, a nonconformally flat form of the geometry can be chosen which allows fairly simple superposition of Kerr holes with arbitrary mass and spin. We present initial data sets representing locally Kerr holes at large separation, and representing rotating holes close enou gh so that outside a common horizon the spacetime geometry is a pertur bation of a single Kerr hole. [S0556-2821(98)09520-3].