Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutrino Flavor Pendulum Reloaded: The Case of Fast Pairwise Conversion   In core-collapse supernovae or compact binary merger remnants,
neutrino-neutrino refraction can spawn fast pair conversion of the type $\nu_e
\bar\nu_e \leftrightarrow \nu_x \bar\nu_x$ (with $x=\mu, \tau$), governed by
the angle-dependent density matrices of flavor lepton number. In a homogeneous
and axially symmetric two-flavor system, all angle modes evolve coherently, and
we show that the nonlinear equations of motion are formally equivalent to those
of a gyroscopic pendulum. Within this analogy, our main innovation is to
identify the elusive characteristic of the lepton-number angle distribution
that determines the depth of conversion with the "pendulum spin." The latter is
given by the real part of the eigenfrequency resulting from the linear
normal-mode analysis of the neutrino system. This simple analogy allows one to
predict the depth of flavor conversion without solving the nonlinear evolution
equations. Our approach provides a novel diagnostic tool to explore the physics
of nonlinear systems.

35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
16
The categories of this paper are: stat
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex