Zilhao, Miguel, Cardoso, Vitor, Herdeiro, Carlos, Lehner, Luis and Sperhake, Ulrich (2012), "Collisions of charged black holes", PHYSICAL REVIEW D, 85, 12.
Abstract: We perform fully nonlinear numerical simulations of charged-black-hole
collisions, described by the Einstein-Maxwell equations, and contrast
the results against analytic expectations. We focus on head-on
collisions of nonspinning black holes, starting from rest and with the
same charge-to-mass ratio, Q/M. The addition of charge to black holes
introduces a new interesting channel of radiation and dynamics, most of
which seem to be captured by Newtonian dynamics and flat-space
intuition. The waveforms can be qualitatively described in terms of
three stages: (i) an infall phase prior to the formation of a common
apparent horizon; (ii) a nonlinear merger phase that corresponds to a
peak in gravitational and electromagnetic energy; (iii) the ringdown
marked by an oscillatory pattern with exponentially decaying amplitude
and characteristic frequencies that are in good agreement with
perturbative predictions. We observe that the amount of
gravitational-wave energy generated throughout the collision decreases
by about 3 orders of magnitude as the charge-to-mass ratio Q/M is
increased from 0 to 0.98. We interpret this decrease as a consequence of
the smaller accelerations present for larger values of the charge. In
contrast, the ratio of energy carried by electromagnetic to
gravitational radiation increases, reaching about 22% for the maximum
Q/M ratio explored, which is in good agreement with analytic
predictions.