# Stability of three neutrino flavor conversion in supernovae

## TL;DR

This paper investigates the stability of three-flavor neutrino oscillations in supernovae, revealing new instabilities for normal mass ordering that differ from previously known inverted ordering cases.

## Contribution

It demonstrates the existence of neutrino flavor conversion instabilities for normal mass ordering in symmetric supernova models, extending prior two-flavor studies.

## Key findings

- Instabilities exist for normal mass ordering in symmetric systems.
- New instability associated with Δm_{21}^2 for normal ordering.
- Growth rates are smaller by about an order of magnitude.

## Abstract

Neutrino-neutrino interactions can lead to collective flavor conversion in the dense parts of a core collapse supernova. Growing instabilities that lead to collective conversions have been studied intensely in the limit of two-neutrino species and occur for inverted mass ordering in the case of a perfectly spherical supernova. We examine two simple models of colliding and intersecting neutrino beams and show, that for three neutrino species instabilities exist also for normal mass ordering even in the case of a fully symmetric system. Whereas the instability for inverted mass ordering is associated with $\Delta m_{31}^2$, the new instability we find for normal mass ordering is associated with $\Delta m_{21}^2$. As a consequence, the growth rate of these new instabilities for normal ordering is smaller by about an order of magnitude compared to the rates of the well studied case of inverted ordering.