Simulations of Fast Neutrino Flavor Conversions with Interactions in Inhomogeneous Media

TL;DR

This paper uses simulations of toy models to explore how inhomogeneous media and various interactions influence fast neutrino flavor conversions, revealing that certain effects can suppress or delay these transformations.

Contribution

It introduces a simulation framework for inhomogeneous neutrino systems including multiple interactions, highlighting their impact on flavor conversion dynamics.

Findings

Medium refractive effects can significantly alter flavor transformations.

Neutral current scattering can suppress or delay flavor conversions.

Inhomogeneous density profiles influence the onset of fast flavor conversions.

Abstract

We investigate toy models for spatial and temporal instabilities in collective neutrino oscillations induced by neutrino self-interactions, with special emphasis on inhomogeneous systems with densities following a profile. Simulations are based on a mathematica program that solves the Liouville equation with or without vacuum terms, refractive terms from a background medium, and neutrino-neutrino forward scattering, in one space dimension and in time. A discrete number of momentum modes are characterized by the neutrino velocity projection on the spatial direction. We also consider the effects of charged current interaction source terms and neutral current scattering contributions. We find that refractive effects from the medium, in particular for density distributions with a profile, and neutral current non-forward scattering off the background medium can strongly influence fast collective flavor transformations. Specifically we find that if both are present, fast flavor conversions can be strongly suppressed or at least delayed.