  We consider a geometric approach to field theory in which torsion is present
in the matter field equations, and we develop the consequences of the
torsion-spin coupling for a pair of single-handed spinors; we show these
interactions to have the structure of a flavour-changing neutral current giving
rise to a mixing for two massless fermion fields: as torsional interactions for
semispinors entail mixing for massless fermions we speculate that this
mechanism could be responsible for oscillations of neutrinos.
