Equilibrium properties of self-interacting neutrinos in the quasi-particle approach

Abstract

In this work a neutrino gas in equilibrium is studied both at T = 0 and at finite temperature.Neutrinos are treated as massive Dirac quasi-particles with two generations. We include selfinteractions among the neutrinos via neutral currents, as well as the interaction with a background of matter. To obtain the equilibrium properties we use Wigner function techniques. To account for corrections beyond the Hartree approximation, we also introduce correlation functions. We prove that, under the quasi-particle approximation, these correlation functions can be expressed as products of Wigner functions. We analyze the main properties of the neutrino eigenmodes in the medium, such as effective masses and mixing angle. We show that the formulae describing these quantities will differ with respect to the case with no self-interactions.

Construction and analysis of a simplified many-body neutrino model

“…We further observe that the frequency of the coherent oscillations agrees with the predictions of the one-particle formalism for a neutrino in the background of M maximally neutrinos (|ν e + |ν µ )/ √ 2 and N − 1 ≃ N neutrinos in the |ν e state. Indeed, the one-particle oscillation Hamiltonian (15) in this case is…”

“…The problem of the flavor evolution in dense neutrino systems continues to receive a significant amount of attention. In addition to the above mentioned papers [1,10,11,12,13], the reader is referred to [14,15,16,17,18,19] for recent progress.…”