Photon Splitting in Strongly Magnetized Plasma

The process of photon splitting, becomes allowed in the presence of strong magnetic field. We calculate the influence of magnetized plasma on the photon splitting absorption coefficient. We calculate the refraction coefficients and polarization vectors with the inclusion of the vacuum terms at an arbitrary value of the magnetic field, and then find photon splitting matrix element taking into account the terms that vanish in vacuum, but may be nonzero in the presence of plasma. We find the photon splitting rate in plasma with the density typical for a neutron star star atmosphere and identify a region of the parameter space where the plasma effects are important.