Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolution of a Bose-Einstein condensate of neutral atoms --- A field
  theoretical approach   The particle distribution in a Bose condensate under the trapping potential
and its time evolution after switching off the trapping potential suddenly are
calculated. We investigate the problem from the viewpoint of quantum field
theory,using a model of self-interacting neutral boson field. Within the
approximation of retainng the most dominant term in the Hamiltonian after
applying the Bogoliubov replacement, we can calculate analytically the particle
distribution as a function of space and time coordinates.

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The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
11
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
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th