WAS THE ELECTROMAGNETIC-SPECTRUM A BLACKBODY SPECTRUM IN THE EARLY UNIVERSE

It is generally assumed that the electromagnetic spectrum in the primo rdial universe was a blackbody spectrum in vacuum. We derive the elect romagnetic spectrum based on the fluctuation-dissipation theorem that describes the electromagnetic fluctuations in a plasma. Our descriptio n includes thermal and collisional effects in a plasma. The electromag netic spectrum obtained differs from a blackbody spectrum in vacuum at low frequencies. In particular, concentrating on the primordial nucle osynthesis era, it has more energy than the blackbody spectrum for fre quencies less than 3 omega(pe) to 6 omega(pe), where omega(pe) is the electron plasma frequency.