Collective flavor conversions are interactions of neutrinos with quantized flavor waves

TL;DR

This paper develops a quantum theory of neutrino flavor oscillations involving quantized flavor waves, revealing mechanisms for fast flavor conversion and proposing kinetic equations to model instability growth without small-scale resolution.

Contribution

It introduces a quantum framework with flavor plasmons (flavomons) and derives kinetic equations that capture fast flavor instability dynamics.

Findings

Emission of flavomons triggers rapid flavor conversion.

Feynman diagram calculations match instability growth rates.

New kinetic equations describe instability evolution efficiently.

Abstract

Collective oscillations in dense neutrino gases (flavor waves) are notable for their instabilities that cause fast flavor conversion. We develop a quantum theory of interacting neutrinos and flavor wave quanta, which are analogous to plasmons, but also carry flavor. The emission or absorption of such flavor plasmons $\psi$, or flavomons, changes the neutrino flavor. When an angular crossing occurs, the process $\nu_\mu\to\nu_e+\psi$ is more rapid than its inverse along the direction of the crossing, triggering stimulated $\psi$ emission and fast instability. Calculating the rate via Feynman diagrams matches the fast instability growth rate. Our novel $\nu$ and $\psi$ kinetic equations, corresponding to quasi-linear theory, describe instability evolution without resolving the small scales of the flavomon wavelength, potentially overcoming the main challenge of fast flavor evolution.