Propagation of transverse electromagnetic waves together with gravitational perturbations in isotropic Universe

Bahaviour of gravitational perturbations together with electromagnetic ones in radiation-dominated plasma in isotropic Universe is considered. It is shown that transverse electromagnetic waves, vector and tensor gravitational perturbations are independent from each other. A law of transverse electromagnetic wave propagation at lepton and radiation-dominated stages is found. It is shown that scalar gravitational perturbations may excite transverse electromagnetic fields in a radiation-dominated plasma