Medium effects in string-dilaton-induced neutrino oscillations

We consider the unconventional way to interpret the current data on solar neutrino oscillations as derived recently by Halprin and Leung from a string model based on the existence of the string dilaton field which remains massless in the low-energy world. The equivalence principle violation entailed by the existence of a massless dilaton may then produce neutrino oscillations even for neutrinos that are degenerate in mass. Here we calculate the medium-induced mass squared difference for solar neutrinos, which is due to their coherent interactions with the cosmic neutrino background and with solar plasma constituents. We show that this difference can naturally be large enough to satisfy the known experimental limits on the Just So solution as well as on the MSW solution of the solar neutrino problem.