Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraining invisible neutrino decays with the cosmic microwave
  background   Precision measurements of the acoustic peaks of the cosmic microwave
background indicate that neutrinos must be freely streaming at the photon
decoupling epoch when T ~ 0.3 eV. This requirement implies restrictive limits
on ``secret neutrino interactions,'' notably on neutrino Yukawa couplings with
hypothetical low-mass (pseudo)scalars \phi. For diagonal couplings in the
neutrino mass basis we find g < 1 x 10^-7, comparable to limits from supernova
1987A. For the off-diagonal couplings and assuming hierarchical neutrino masses
we find g < 1 x 10^-11 (0.05 eV/m)^2 where m is the heavier mass of a given
neutrino pair connected by g. This stringent limit excludes that the flavor
content of high-energy neutrinos from cosmic-ray sources is modified by \nu ->
\nu' + \phi decays on their way to Earth.

2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci