Neutrinos from dense environments : Flavor mechanisms, theoretical approaches, observations, and new directions

TL;DR

This paper reviews the mechanisms of neutrino flavor transformation in dense astrophysical environments, discussing theoretical models, observational implications, and future research directions in understanding supernovae and related phenomena.

Contribution

It provides a comprehensive overview of flavor mechanisms, theoretical approaches, and observational prospects for neutrinos in dense environments, highlighting new research directions.

Findings

Neutrino interactions significantly alter flavor in dense astrophysical settings.

Theoretical models range from mean-field to quantum kinetic equations.

Understanding neutrino flavor changes aids in supernova explosion models and neutrino observations.

Abstract

Neutrino masses and mixings produce vacuum oscillations, an established quantum mechanical phenomenon. In matter, the Mikheev-Smirnov-Wolfenstein effect, due to neutrino interactions with the background particles, triggers resonant flavor modification. In dense environments, such as core-collapse supernovae or compact mergers, sizable neutrino-neutrino interactions, shock waves and turbulence impact the neutrino flavor content under a variety of phenomena. Theoretical approaches of neutrino propagation range from the mean-field approximation to the full quantum kinetic equations. Intriguing connections have been uncovered between weakly interacting dense neutrino gases and other many-body systems and domains, from condensed matter and nuclear physics to quantum computing. Besides the intrinsic theoretical interest, establishing how neutrinos change flavor contributes to answer the longstanding open questions of how massive stars explode and of the r-process sites. It is also important for future observations of core-collapse supernova neutrinos and of the diffuse supernova neutrino background that should be discovered in the foreseeable future.