  Photons, as quanta of electromagnetic fields, determine the electromagnetic
properties of an extremely hot and dense medium. Considering the properties of
photons in the interacting medium of charged particles, we explicitly calculate
the electromagnetic properties such as the electric permittivity, magnetic
permeability, refractive index and the propagation speed of electromagnetic
signals in extremely hot and dense background in cosmos. Photons acquire
dynamically generated mass in a medium. The screening mass of photon, Debye
shielding length and the plasma frequency are calculated as functions of
statistical parameters of the medium. We study the properties of the
propagating particles in astrophysical systems of distinct statistical
conditions. The modifications in the medium properties lead to the equation of
state of the system. We mainly calculate all these parameters for extremely
high temperatures of the early universe.
