Strange mechanics of the neutrino flavor pendulum
  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.
