Negative euclidean action, instantons and pair creation in strong background fields

Abstract

The creation of scalar bosons is studied in background fields which make the effective mass of the scalar field imaginary in a finite region of space-time. The number of created particles in the semiclassical approximation is shown to be exp(- S E inst ) is the euclidean action evaluated at the instanton-like-solution in the theory of a relativistic point particle with the proper time rotated to the euclidean domain, τ → -⇔ τ. The instanton action is negative, so that the number of created particles is exponentially large. The most probable trajectory of created particles is shown to be the analytical continuation of the instanton trajectory back to real proper time.