Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar neutrino spectrum, sterile neutrinos and additional radiation in
  the Universe   Recent results from the SNO, Super-Kamiokande and Borexino experiments do not
show the expected upturn of the energy spectrum of events (the ratio $R \equiv
N_{obs}/N_{SSM}$) at low energies. At the same time, cosmological observations
testify for possible existence of additional relativistic degrees of freedom in
the early Universe: $\Delta N_{eff} = 1 - 2$. These facts strengthen the case
of very light sterile neutrino, $\nu_s$, with $\Delta m^2_{01} \sim (0.7 - 2)
\cdot 10^{-5}$ eV$^2$, which mixes weakly with the active neutrinos. The
$\nu_s$ mixing in the mass eigenstate $\nu_1$ characterized by $\sin^2 2\alpha
\sim 10^{-3}$ can explain an absence of the upturn. The mixing of $\nu_s$ in
the eigenstate $\nu_3$ with $\sin^2 \beta \sim 0.1$ leads to production of
$\nu_s$ via oscillations in the Universe and to additional contribution $\Delta
N_{eff} \approx 0.7 - 1$ before the big bang nucleosynthesis and later. Such a
mixing can be tested in forthcoming experiments with the atmospheric neutrinos
as well as in future accelerator long baseline experiments. It has substantial
impact on conversion of the supernova neutrinos.

29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat