In the context of the Einstein-Cartan-Dirac model, where the torsion of the
space-time couples to the axial currents of the fermions, we study the effects
of this quantum-gravitational interaction on a massless neutrino beam crossing
through a medium with high number density of fermions at rest. We calculate the
reflection amplitude and show that a specific fraction of the incident
neutrinos reflects from this potential if the polarization of the medium is
different from zero. We also discuss the order of magnitude of the fermionic
number density in which this phenomenon is observable, in other theoretical
contexts, for example the strong-gravity regime and the effective field theory
approach.Comment: 8 pages, LaTe