Head-on collision of two equal mass black holes

Abstract

We study the head-on collision of two equal mass nonrotating black holes. Various initial configurations are investigated, including holes which are initially surrounded by a common apparent horizon to holes that are separated by about 20M, where M is the mass of a single black hole. We have extracted both l=2 and l=4 gravitational waveforms resulting from the collision. The normal modes of the final black hole dominate the spectrum in all cases studied. The total energy radiated is computed using several independent methods, and is typically less than 0.002M. We also discuss an analytic approach to estimate the total gravitational radiation emitted in the collision by generalizing point particle dynamics to account for the finite size and internal dynamics of the two black holes. The effects of the tidal deformations of the horizons are analyzed using the membrane paradigm of black holes. We find excellent agreement between the numerical results and the analytic estimates.