  We discuss new bounce-like (but non-time-reversal-invariant-) solutions to
Euclidean equations of motion, which we dub boomerons. In the Euclidean path
integral approach to quantum theories, boomerons make an imaginary contribution
to the vacuum energy. The fake vacuum instabilty can be removed by cancelling
boomeron contributions against contributions from time reversed boomerons
(anti-boomerons). The cancellation rests on a sign choice whose significance is
not completely understood in the path integral method.
