  In single-bubble sonoluminescence, a bubble trapped by a sound wave in a
flask of liquid is forced to expand and contract; exactly once per cycle, the
bubble emits a very sharp ($< 50 ps$) pulse of visible light. This is a robust
phenomenon observable to the naked eye, yet the mechanism whereby the light is
produced is not well understood. One model that has been proposed is that the
light is "vacuum radiation" generated by the coupling of the electromagnetic
fields to the surface of the bubble. In this paper, we simulate vacuum
radiation by solving Maxwell's equations with an additional term that couples
the field to the bubble's motion. We show that, in the static case originally
considered by Casimir, we reproduce Casimir's result. In a simple purely
time-dependent example, we find that an instability occurs and the pulse of
radiation grows exponentially. In the more realistic case of
spherically-symmetric bubble motion, we again find exponential growth in the
context of a small-radius approximation.
