  Plasma supports electromagnetic waves propagation for frequencies higher than
plasma frequency but features dielectric permittivity less than 1. This
property leads to photon density of states (DOS) lower than in vacuum and
should result in subnatural spectral linewidths, sub-Planckian spectrum of
thermal radiation, and sub-Rayleigh scattering as well as in lower inelastic
photon scattering including Raman scattering. Lamb shift will be altered as
well though the decisive contribution from high-energy modes in this case makes
the photon DOS effect rather small since plasma DOS converges with the vacuum
one in the limit of infinite frequencies. We emphasize the basic character of
all these phenomena though absolute values of corrections in many real
experiments may appear to be small as compared to other factors. We found that
dissipative losses make possible DOS effects smaller though not vanishing and
additionally bring about indefinite growth of DOS in the low-frequency limit.
