Stationary solutions for fast flavor oscillations of a homogeneous dense neutrino gas

We present a method to find the stationary solutions for fast flavor oscillations of a homogeneous dense neutrino gas. These solutions correspond to collective precession of all neutrino polarization vectors around a fixed axis in the flavor space on average, and are conveniently studied in the co-rotating frame. We show that these solutions can account for the numerical results of explicit evolution calculations, and that even with the simplest assumption of adiabatic evolution, they can provide the average survival probabilities to good approximation. We also discuss improvement of these solutions and their use as estimates of the effects of fast oscillations in astrophysical environments. (C) 2021 The Authors. Published by Elsevier B.V.