Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exciton condensation in quantum wells. Exciton hydrodynamics. The effect
  of localized states   The hydrodynamic equations for indirect excitons in the double quantum wells
are studied taking into account 1) a possibility of an exciton condensed phase
formation, 2) the presence of pumping, 3) finite value of the exciton lifetime,
4) exciton scattering by defects. The threshold pumping emergence of the
periodical exciton density distribution is found. The role of localized and
free exciton states is analyzed in the formation of emission spectra.

28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol