Approximations to the QED Fermion Greens Function in a Constant External Field


Abstract in English

An exact representation of the causal QED fermion Greens function, in an arbritrary external electromagnetic field, derived by Fried, Gabellini and McKellar, and which naturally allows for non-perturbative approximations, is here used to calculate non-perturbative approximations to the Greens function in the simple case of a constant external field. Schwingers famous exact result is obtained as the limit as the order of the approximation approaches infinity.

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