Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Local invariants in effective hydrodynamics of trapped dilute-gas
  Bose-Einstein condensates   In the framework of mean-field approximation the dynamics of Bose-Einstein
condensates can be described by the hydrodynamic-like equations. These
equations are analyzed here with account of mutual interaction between
condensate and non-condensate atoms. The Lagrange invariants and freezing-in
invariants of such a system have been found. This allows to get some necessary
conditions for creation of an atom laser with controlled parameters of the
beam. Particularly, the atom laser beam can carry quite well defined angular
momentum. This can be practically realized in the most simple case, when the
vorticity of condensate appears to be a freezing-in field. The optimal
conditions for a source mode regime are found out in the paper.

9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph