Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the stability of the coherent state of a two-level atom Bose gas in
  the resonant laser field at zero temperature   It is shown that a Bose gas of two-level atoms in the intense resonant laser
field at zero temperature is a mixture of two condensates with a definite ratio
of the densities. The criteria of stability are found for the stationary states
of such system against the increment of the amplitudes of quasi Bogoliubov
elementary excitations. Besides the usual acoustic mode the gap mode is shown
to exist and the magnitude of the gap is proportional to the laser field
amplitude. The involvement of the gas nonideality under definite conditions
results in an instability and decay of the condensates.

33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph