Equilibrium radiation in a plasma medium with spatial and frequency dispersion

Examination of equilibrium radiation in plasma media shows that the spectral energy distribution of such radiation differs from that of Planck equilibrium radiation. Using the quantum electrodynamic approach, the general relation for the spectral energy density of equilibrium radiation in a system of charged particles is found. The obtained result takes into account the influence of plasma on equilibrium radiation through the explicit transverse dielectric permittivity which includes spatial and frequency dispersion, as well as the finite collision damping. For the limiting case of infinitesimal damping the result is identical with the known expression.