K-essence Interactions with Neutrinos: Flavor Oscillations without Mass – Christopher Gauthier

Date: Tue. December 7th, 2010, 11:30 am-12:30 pm
Location: Rockefeller 221

In this talk we discuss a novel means of coupling neutrinos to a Lorentz violating background k-essence field. K-essence is a model of dark energy, which uses a non-canonical scalar field to drive the late time accelerated expansion of the universe. We propose that neutrinos couple to the k-essence induced metric rather than the space-time metric. The immediate effect that this has will be to modify the energy-momentum relation of the neutrino. This implies that the neutrino velocity will in general be different from the speed of light, even if the neutrino is massless. Later we will see that k-essence can also induce neutrino oscillations even without a neutrino mass term. It will be shown that if k-essence couples non-diagonally to the neutrino flavor eigenstates, then this leads to an oscilation length that varies inversely with the neutrino energy. This should be contrasted with the case of purely mass induced neutrino oscillations which result in a different behavior. Thus k-essence induced neutrino oscillations have a very different observational signature than neutrino oscillations created by mass. However, observations favor a leading order lambda propto E behavior. While k-essence induced neutrino oscillation are not favored experimentally, our result places tight constraints on the possible interaction that a k-essence background can have with neutrinos. All non-trivial physical effects discussed here require the sound speed of k-essence fluctuations to be different from the speed of light, and hence are primarily a consequence of Lorentz violation.