MAGNETOHYDRODYNAMICS IN THE EXPANDING UNIVERSE

We present a comprehensive study of the magnetohydrodynamic (MHD) mode s and corresponding state eigenvectors in the early Universe. The flui d equations are formulated using the 3+1 formalism of Thorne and MacDo nald, as utilized by us in our previous work. The equations are then s olved in various regimes. The first of these is the ultrarelativistic limit, where we study the electron-positron plasma at high temperature s. Here, we find the conformal invariance property of the metric ensur es results very similar to those of hat spacetime. We also investigate an electron-proton fluid before and after recombination, where a nonr elativistic limit suffices. Here the various frequencies redshift at d ifferent rates with respect to one another, which complicates the solu tions considerably. A thorough discussion, both quantitative and quali tative, is given for all solutions obtained.