We perform fully non-linear 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 non-spinning 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 which 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 three 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 .