MG11 
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Pair creation in inhomogeneous fields

It has been known since the early days of QED that spontaneous electron-positron pair creation from vacuum should occur in a strong electric field. A simple formula for the pair creation rate in the constant field case was obtained in 1951 by Schwinger using effective action methods. However, many potential applications such as in laser or heavy ion physics involve electric fields which are strongly inhomogeneous. After a short review of those results which exist in the literature for special cases of inhomogeneous fields, I will present a recently developed approach to this problem based on a stationary phase approximation of Feynman's relativistic worldline path integral representing the one-loop QED effective action in the field. For a large class of fields the stationary paths can be given explicitly, and the determinant of fluctuations around them be calculated using the Gelfand-Yaglom technique. This allows one to obtain the pair creation rate in a simple and elegant way. The relation to standard WKB methods is shortly discussed.