Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutrino refraction by the cosmic neutrino background   We have determined the dispersion relation of a neutrino test particle
propagating in the cosmic neutrino background. Describing the relic neutrinos
and antineutrinos from the hot big bang as a dense medium, a matter potential
or refractive index is obtained. The vacuum neutrino mixing angles are
unchanged, but the energy of each mass state is modified. Using a matrix in the
space of neutrino species, the induced potential is decomposed into a part
which produces signatures in beta-decay experiments and another part which
modifies neutrino oscillations. The low temperature of the relic neutrinos
makes a direct detection extremely challenging. From a different point of view,
the identified refractive effects of the cosmic neutrino background constitute
an ultralow background for future experimental studies of nonvanishing Lorentz
violation in the neutrino sector.

15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int