Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Damped quantum harmonic oscillator: density operator and related
  quantities   A closed expression for the density operator of the damped harmonic
oscillator is extracted from the master equation based on the Lindblad theory
for open quantum systems. The entropy and effective temperature of the system
are subsequently calculated and their temporal behaviour is surveyed by showing
how these quantities relax to their equilibrium values. The entropy for a state
characterized by a Wigner distribution function which is Gaussian in form is
found to depend only on the variance of the distribution function.

35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an