Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The impact of excited neutrinos on $\nu \bar{\nu}\to \gamma\gamma$
  process   We examine the effect of excited neutrinos on the annihilation of relic
neutrinos with ultra high energy cosmic neutrinos for the $\nu \bar{\nu}\to
\gamma\gamma$ process. The contribution of the excited neutrinos to the
neutrino-photon decoupling temperature are calculated. We see that
photon-neutrino decoupling temperature can be significantly reduced below the
obtained value of the Standard Model with the impact of excited neutrinos.

34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con