On analytic properties of the photon polarization function in a backgroundmagnetic field

We examine the analytic properties of the photon polarization function in a background magnetic field, using the technique of inverse Mellin transform . The photon polarization function is first expressed as a power series of the photon energy omega with omega < 2m(e). Based upon this energy expansio n and the branch cut of the photon polarization function in the complex ome ga plane. we compute the absorptive part of the polarization function with the inverse Mellin transform. Our results are valid for arbitrary photon en ergies and magnetic-fieid strengths. The applications of our approach are b riefly discussed. (C) 2001 Published by Elsevier Science B.V.