PHOTON SPLITTING IN STRONG MAGNETIC-FIELDS

Using the formalism of relativistic quantum field theory we derive the probability for the splitting of one photon into two photons in the p resence of a uniform magnetic field, We express the electron propagato r in a magnetic field in terms of Landau spinors in configuration spac e and obtain an analytical expression for the S-matrix element of the third-order process which is exact in the magnetic field strength as w ell as the photon energy, and lends itself to numerical evaluation. Nu merical results are presented for the splitting probability as a funct ion of photon energy below the pair creation threshold for different n eutron star magnetic field strengths. Our results open the way to quan titative studies of the signature of photon splitting in the gamma-ray spectra of compact cosmic objects.