Sufficient and Necessary Conditions for Collective Neutrino Instability: Fast, Slow, and Mixed

TL;DR

This paper establishes comprehensive criteria for the occurrence of collective neutrino flavor instabilities, considering complex initial distributions dependent on energy and angle, with significant implications for astrophysics.

Contribution

It provides the first general instability conditions for neutrino distributions depending on both energy and emission angle, advancing understanding of neutrino flavor conversions.

Findings

Derived necessary and sufficient conditions for neutrino flavor instability.

Applicable to complex energy and angle-dependent distributions.

Enhances predictive capabilities for astrophysical neutrino phenomena.

Abstract

Collective neutrino oscillations exhibit instabilities that induce appreciable flavor conversion, with crucial astrophysical implications. While the importance of initial phase-space distributions is well-established, a general instability criterion for distributions dependent on both energy and emission angle has been lacking. We identify and analyze the sufficient (and necessary) conditions for a generic collective neutrino flavor instability.