Electrical conductivity in the early universe

We calculate the electrical conductivity in the early universe at temperatures below as well as above the electroweak vacuum scale, T-c=100 GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, sigma(el)similar to T/alpha In(1/alpha), at temperatures well below T-c. At temperatures above, W+/- charge-exchange processes-analogous to color exchange through gluons in QCD-effectively stop left-handed charged leptons. However, right-handed leptons can carry current, resulting in sigma(el)/T being only a factor similar to cos(4) theta(W) Smaller than at temperatures below T-c. [S0556-2821(97)06620-4].