Stringent constraint on the scalar-neutrino coupling constant from quintessential cosmology

An extremely light (m(phi) much less than 10(-33) eV), slowly-varying scala r field phi (quintessence) with a potential energy density as large as 60% of the critical density has been proposed as the origin of the accelerated expansion of the universe at present. The interaction of this smoothly dist ributed component with another predominantly smooth component, the cosmic n eutrino background, is studied. The slow-roll approximation for generic phi potentials may then be used to obtain a limit on the scalar-neutrino coupl ing constant, found to be many orders of magnitude more stringent than the limits set by observations of neutrinos from SN 1987A. In addition, if quin tessential theory allows for a violation of the equivalence principle in th e sector of neutrinos, the current solar neutrino data can probe such a vio lation at the 10(-10) level.