The Instantonic Approach with Non-Equivalent Vacua
  We study the quantum-mechanical tunneling phenomenon in models which include the existence of non-equivalent vacua. For such a purpose we evaluate the euclidean propagator between two minima of the potential at issue in terms of the quadratic fluctuations over the corresponding instantons. The effect of the multi-instanton configurations are included by means of the alternate dilute-gas approximation. 
J. Casahorran (University of Zaragoza, Spain)