Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the question of radiative losses in the frame of density matrix
  formalism in free space   The problem of radiative losses is usually considered using harmonic
oscillator model for quantum dynamics. It is shown that this evidently wrong
approach nevertheless cannot be straightforwardly improved by direct
substitution of the harmonic oscillator by density matrix equations.

35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess