THE IMAGINARY-TIME PATH-INTEGRAL AND NON-TIME-REVERSAL-INVARIANT SADDLE-POINTS OF THE EUCLIDEAN ACTION

We discuss new bounce-like (but non-time-reversal-invariant) solutions to Euclidean equations of motion, which we dub boomerons. In the Eucl idean path integral approach to quantum theories, boomerons make an im aginary contribution to the vacuum energy. The fake vacuum instability can be removed by cancelling boomeron contributions against contribut ions from time reversed boomerons (anti-boomerons). The cancellation r ests on a sign choice whose significance is not completely understood in the path integral method. (C) 1998 Elsevier Science B.V.