2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/168622The fermion spin-flip conversion $f_L \to f_R + γ$ is considered, caused by the difference of the additional energies of the electroweak origin, acquired by left- and right-handed fermions (neutrino, electron) in medium. An accurate taking account of the fermion and photon dispersion in medium is shown to be important.5 pages, LaTeX, 1 PS figure, based on the talk presented by A.V. Kuznetsov at the XV International Seminar Quarks'2008, Sergiev Posad, Moscow Region, May 23-29, 2008, to appear in the ProceedingsHigh Energy Physics - Phenomenologytext