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, Tc100GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, σₑₗ~T/αln(1/α), at temperatures well below Tc. 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 σₑₗ/T being only a factor ~cos⁴θW smaller than at temperatures below Tc.