Flavor isospin waves in one-dimensional axisymmetric neutrino gases

TL;DR

This paper demonstrates the existence of coherent flavor isospin wave solutions in one-dimensional axisymmetric neutrino gases, providing insights into the nonlinear behavior of fast neutrino oscillations relevant to supernovae and neutron star mergers.

Contribution

It introduces nontrivial solutions to the flavor equations of motion that describe flavor isospin waves, extending understanding beyond linear dispersion relations.

Findings

Existence of flavor isospin wave solutions in 1D axisymmetric neutrino gases

Computed dispersion relations for these waves in specific cases

Insights into the nonlinear evolution of fast neutrino oscillations

Abstract

Flavor oscillations can occur on very short spatial and temporal scales in the dense neutrino media in a core-collapse supernova (CCSN) or binary neutron star merger (BNSM) event. Although the dispersion relations (DRs) of the fast neutrino oscillations can be obtained by linearizing the equations of motion (EoM) before the emergence of any significant flavor conversion, one largely depends on numerical calculations to understand this interesting phenomenon in the nonlinear regime. In this work we demonstrate that there exist nontrivial solutions to the flavor EoM that govern the fast oscillations in one-dimensional axisymmetric neutrino gases. These solutions represent a coherent flavor isospin wave similar to the magnetic spin wave in a lattice of magnetic dipoles. We also compute the DRs of such waves in some example cases which are closely related to the DRs of the fast neutrino oscillations obtained in the linear regime. This result sheds new light on the long-term behavior of fast neutrino oscillations which can have various implications for the CCSN and BNSM events.