Lifetime and decay of "excited vacuum" states of a field theory associated with nonabsolute minima of its effective potential

We discuss the decay of the excited vacuum states of a field theory associated with the nonabsolute minima of its effective potential. Using the equivalence of the sine-Gordon theory in (1+1) dimensions to Thirring fermion theory we demonstrate explicitly the nature of one such decay and compute its lifetime. The fact that ordinary perturbation theory cannot be used to describe the decay is also examined.