2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185051We review the Floquet theory of linear differential equations with periodic coefficients and discuss its applications to neutrino oscillations in matter of periodically varying density. In particular, we consider parametric resonance in neutrino oscillations which can occur in such media, and discuss implications for oscillations of neutrinos traversing the earth and passing through the earth's core.LaTeX, 28 pages, 8 eps figures. Contribution to the special issue of Yad. Fiz. dedicated to the memory of A.B. MigdalHigh Energy Physics - PhenomenologyAstrophysicsHigh Energy Physics - Theorytext