PLASMA ELECTRODYNAMICS IN THE EXPANDING UNIVERSE

The 3+1 formalism of Thorne and Macdonald is used to formulate the ele ctrodynamic equations for a plasma in a spatially hat Robertson-Walker metric. The conformal flatness of this spacetime ensures that these e quations closely mirror those of hat space-time, The linearized Vlasov Maxwell equations are solved for the case of an unmagnetized plasma o f ultrarelativistic particles and antiparticles, and the results are c ompared with those of classical kinetic theory and quantum field theor y in special relativity. The Vlasov-Maxwell equations for a plasma of nonrelativistic particles are not conformally invariant, so a fluid ap proximation is used to obtain the linear modes of oscillation, again f or an unmagnetized plasma. The plasma modes redshift at rates which de pend on the rate of expansion of the Universe, and whether the electro magnetic fields or the particles dominate the dynamics.