  The first fully non-linear numerical simulations of colliding charged black
holes in D=4 Einstein-Maxwell theory were recently reported arXiv:1205.1063.
These collisions were performed for black holes with equal charge-to-mass
ratio, for which initial data can be found in closed analytic form. Here we
generalize the study of collisions of charged black holes to the case of
unequal charge-to-mass ratios. We focus on oppositely charged black holes, as
to maximize acceleration-dependent effects. As |Q|/M increases from 0 to 0.99,
we observe that the gravitational radiation emitted increases by a factor of ~
2.7; the electromagnetic radiation emission becomes dominant for |Q|/M >~ 0.37
and at |Q|/M=0.99 is larger, by a factor of ~ 5.8, than its gravitational
counterpart. We observe that these numerical results exhibit a precise and
simple scaling with the charge. Furthermore, we show that the results from the
numerical simulations are qualitatively captured by a simple analytic model
that computes the electromagnetic dipolar radiation and the gravitational
quadrupolar radiation of two non-relativistic interacting particles in
Minkowski spacetime.
