Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modification of The Transition Rate in The Hydrogen Atom placed in
  Finite Space   When a hydrogen atom trapped in finite space formed by two parallel perfectly
conducting plates, the transition rates can be modified. Life-time of the
hydrogen $2P_{1/2}$-state is estimated to be shorter as much as $56.3ps $ with
a separation distance of $b = 1.2 \mu m$ between two plates. Although the
modification is dependent on position of the atom, the life-time can be shorten
or lengthen by adjusting the separation distance even for the case that the
atom is placed at the center between two plates.

14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph