  We consider noise-driven exit from a domain of attraction in a
two-dimensional bistable system lacking detailed balance. Through analog and
digital stochastic simulations, we find a theoretically predicted bifurcation
of the most probable exit path as the parameters of the system are changed, and
a corresponding nonanalyticity of the activation energy. We also investigate
the extent to which the bifurcation is related to the local breaking of
time-reversal invariance.
