Symmetry breaking, and the effect of matter density on neutrino oscillation

Understand

A proposal for the neutrino mass, based on neutrino-scalar field interaction, is introduced.

• The scalar field is also non-minimally coupled to the Ricci scalar and hence relates the neutrino mass to the matter density.
• In a dense region, the scalar field obeys the $Z_2$ symmetry, and the neutrino is massless.
• In a dilute region, the $Z_2$ symmetry breaks and neutrino acquires mass from the non-vanishing expectation value of the scalar field.