We discuss the gauge parameter dependence of particle spectra in statistical quantum electrodynamics and conclude that the electron spectrum is gaugeparameter dependent. The physical spectrum being obtained in the Landau gauge, which leads to gauge invariance in a restricted class of gauge transformations. We compute the thermal self-energy of electrons in a dense media to first order in the fine structure constant. In the zero-temperature limit and at high density the dispersion equation is solved for some gauges, the curves differing from that corresponding to the physical transverse gauge.

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We compute the dispersion curves for neutrinos propagating in a very dense electroweak plasma, in magnetic fields of order [Formula: see text]. The neutrino self-energy is calculated in the one-loop approximation. The dispersion equation is solved for motion parallel and perpendicular to the external magnetic field. We obtain an effective neutrino mass which increases with the magnetic field, up to values B where threshold energy for creation of W± pairs (out from the thermal background) is reached.