# New effects of non-standard self-interactions of neutrinos in a supernova

## TL;DR

This paper explores how non-standard self-interactions of neutrinos can induce new flavor conversion effects in supernovae, potentially affecting neutrino signals during neutronization bursts.

## Contribution

It reveals novel effects of non-standard neutrino self-interactions on flavor oscillations, including flavor instability in normal hierarchy and spectral swap modifications.

## Key findings

- Flavor instability can occur in normal hierarchy due to NSSI.
- Flavor-preserving NSSI cause spectral swap pinching.
- Flavor-violating NSSI induce swaps without spectral crossings.

## Abstract

Neutrino self-interactions are known to lead to non-linear collective flavor oscillations in a core-collapse supernova. We point out new possible effects of non-standard self-interactions (NSSI) of neutrinos on flavor conversions in a two-flavor framework. We show that, for a single-energy neutrino-antineutrino ensemble, a flavor instability is generated even in normal hierarchy for large enough NSSI. Using a toy model for the neutrino spectra, we show that flavor-preserving NSSI lead to pinching of spectral swaps, while flavor-violating NSSI cause swaps to develop away from a spectral crossing or even in the absence of a spectral crossing. Consequently, NSSI could give rise to collective oscillations and spectral splits even during neutronization burst, for both hierarchies.