Expressions, accurate to the first order in $e^2$, are obtained for the charge and current densities which, according to positron theory, are induced in vacuum by an electromagnetic field. Because the corresponding correction terms in the Maxwell field equations involve integral operators, it does not seem possible to treat the modified field equations by Hamiltonian methods.

• Received 24 April 1935

DOI:https://doi.org/10.1103/PhysRev.48.49