Worldline instantons, vacuum pair production and Gutzwiller's trace formula**Plenary talk at QFEXT07 (Quantum Fields Under External Conditions), Leipzig, September 2007.

Abstract

In this talk, I describe a new application of the Gutzwiller trace formula formalism, to give a compact expression for the semiclassical vacuum pair production rate in quantum electrodynamics, for general inhomogeneous electromagnetic background fields. The semiclassical rate is expressed in terms of geometric properties of classical periodic phase space orbits for the associated Euclidean problem of propagation of a charged particle in the inhomogeneous background field, parametrized by the proper time.