Comment on "Energy of a plasma in the classical limit"

Merav Opher* and Reuven Opher Instituto Astronômico e Geofı́sico–IAGyUSP, Avenida Miguel Stéfano, 4200, CEP 04301-904 São Paulo, S.P., Brazil (Received 4 January 1999; revised manuscript received 15 March 1999) When lT ø dT , where lT is the de Broglie wavelength and dT is the distance of closest approach of thermal electrons, a classical analysis of the energy of a plasma can be made. In all the classical analysis made until now, it was assumed that the frequency of the fluctuations v ø T , (kB ­ h̄ ­ 1). Using the fluctuation-dissipation theorem, we evaluate the energy of a plasma, allowing the frequency of the fluctuations to be arbitrary. We find that the energy density is appreciably larger than previously thought for many interesting plasmas, such as the plasma of the Universe before the recombination era. [S0031-9007(99)09376-X]