Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reason for the large scale differences in the results for the
  neutron-antineutron oscillation problem   It is shown that there is a double counting in the standard model of $n\bar
{n}$ mixing in the medium, resulting in full cancellation of leading terms. The
direct calculation of $n\bar{n}$ transition followed by annihilation is
performed. The lower limit for the free-space $n\bar{n}$ oscillation time is
$\tau_{n\bar{n}} \sim T_{n\bar{n}}>10^{16}y$, where $T_{n\bar{n}}$ is the
lifetime of neutron bound in a nucleus. This limit exceeds the previous one by
16 orders of magnitude.

27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph