Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamics of small perturbations against a stationary polariton
  distribution   The dynamics of small perturbations against the stationary density matrix of
a pumped polariton system with only one photon polarization is studied.
Depending on the way the system is pumped and probed, decay times ranging from
30 to 5000 ps are found. The large decay times under resonant pumping are
related to a bottleneck effect in the decay of the excess (probe) populations
of dark polariton states. No singular behaviour at the threshold for polariton
lasing is observed.

18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org