Strange mechanics of the neutrino flavor pendulum

TL;DR

This paper explores novel phenomena in neutrino flavor transformation, revealing a mechanical analogy to a gyroscopic pendulum that exhibits counterintuitive behaviors, with implications for astrophysics and dark matter.

Contribution

It introduces a new class of flavor transformation phenomena in neutrinos, modeled as a gyroscopic pendulum showing unexpected precession behaviors, and connects these to astrophysical contexts.

Findings

Identification of a new class of neutrino flavor phenomena

Mechanical analogy with a gyroscopic pendulum explains behaviors

Potential implications for dark matter and astrophysical environments

Abstract

We identify in the flavor transformation of astrophysical neutrinos a new class of phenomena, a common outcome of which is the suppression of flavor conversion. Appealing to the equivalence between a bipolar neutrino system and a gyroscopic pendulum, we find that these phenomena have rather striking interpretations in the mechanical picture: in one instance, the gyroscopic pendulum initially precesses in one direction, then comes to a halt and begins to precess in the opposite direction---a counterintuitive behavior that we analogize to the motion of a toy known as a rattleback. We analyze these behaviors in the early universe, wherein a chance connection to sterile neutrino dark matter emerges, and we briefly suggest how they might manifest in compact-object environments.