Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Theory of a stable strong electrostatic double layer generated in a
  two-grid Franck-Hertz tube
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin