Linearizing neutrino evolution equations including neutrino-antineutrino pairing correlations

TL;DR

This paper develops a linearized framework for neutrino evolution equations, incorporating neutrino-antineutrino pairing correlations, to identify instabilities and analyze quasi-particle states in complex environments.

Contribution

It introduces a generalized linearization method for neutrino equations including pairing correlations, extending previous models and enabling analysis of instabilities and quasi-particle spectra.

Findings

Derived eigenvalue equations for neutrino and antineutrino quasi-particles.

Showed that the extended Hamiltonian can be diagonalized with a generalized Bogoliubov-Valatin transformation.

Applicable to multiple neutrino flavors and arbitrary evolution points.

Abstract

We linearize the neutrino mean-field evolution equations describing the neutrino propagation in a background of matter and of neutrinos, using techniques from many-body microscopic approaches. The procedure leads to an eigenvalue equation that allows to identify instabilities in the evolution, associated with a change of the curvature of the neutrino energy-density surface. Our result includes all contributions from the neutrino Hamiltonian and is generalizable to linearize the equations of motion at an arbitrary point of the evolution. We then consider the extended equations that comprise the normal mean field as well as the abnormal mean field that is associated with neutrino-antineutrino pairing correlations. We first re-derive the extended neutrino Hamiltonian and show that such a Hamiltonian can be diagonalized by introducing a generalized Bogoliubov-Valatin transformation with quasi-particle operators that mix neutrinos and antineutrinos. We give the eigenvalue equations that determine the energies of the quasi-particles eigenstates. Finally we derive the eigenvalue equation of the extended equations of motion, valid in the small amplitude approximation. Our results apply to an arbitrary number of neutrino families.