ON THE LOCAL DESCRIPTION OF PAIR PRODUCTION IN INHOMOGENEOUS EXTERNALFIELDS

Particle production in inhomogeneous external fields is studied for th e case of a purely scalar theory. Starting from the proper time formal ism and an approximation valid for slowly varying fields it is shown h ow the interpretation of the effective Lagrangian as a local observabl e quantity affects Lorentz covariance and causal boundary conditions. Using the imaginary part of a suitably modified effective Lagrangian a s a local pair production rate, large discrepancies between perturbati ve and nonperturbative total pair production probabilities are found f or a model external field that is inhogeneous both in space and time. (C) 1994 Academic Press, Inc.