High-velocity collision of two black holes

We study nonaxisymmetric collision of two black holes (BHs) with a high velocity v=|dxⁱ/dx⁰|=0ex0ex0.6c--0.9c at infinity, where x^μ denotes four-dimensional coordinates. We prepare two boosted BHs for the initial condition which is different from that computed by a simple moving-puncture approach. By extrapolation of the numerical results, we find that the impact parameter has to be smaller than ≈2.5GM₀/c² for formation of a BH in the collision for v→c, where M₀c² is the initial total Arnowitt-Deser-Misner energy of the system. For the critical value of the impact parameter, 20%--30% of mass energy and 60%--70% of angular momentum are dissipated by gravitational radiation for $v=0.6c--0.9c$.