Lepton-Number Crossings are Insufficient for Flavor Instabilities
Abstract
In dense neutrino environments, the mean field of flavor coherence can develop instabilities. A necessary condition is that the flavor lepton number changes sign as a function of energy and/or angle. Whether such a crossing is also sufficient has been a longstanding question. We construct an explicit counterexample: a spectral crossing without accompanying flavor instability, with an even number of crossings being key. This failure is physically understood as Cherenkov-like emission of flavor waves. If flipped-lepton-number neutrinos never dominate among those kinematically allowed to decay, the waves cannot grow.
Fields of Study & Subjects
Neutrino Physics Research
Particle physics theoretical and experimental studies
Astrophysics and Cosmic Phenomena
Publication details
- Journal / source
- Physical Review Letters
- Publisher
- American Physical Society (APS)
- Volume
- 136
- Issue
- 5
- Pages
- 051001–051001
- Publication date
- 2 January 2026
- Language
- EN