Electrical conductivity in the early universe

We solve numerically the Boltzmann equation in the early universe in the presence of a constant electric field and find the electrical conductivity σ in the range 1 MeV ≲ T ≲ MW. The main contribution to σ is shown to be due to leptonic interactions. For T ≲ 100 MeV we find σ ⋍ 0.76T while at T ⋍ MW we obtain σ ⋍ 6.7T