Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Atomic Theory of the Two-fluid Model: Broken Gauge Symmetry in
  Bose-Einstein condensation   We discuss the collective excitations in a spatially inhomogeneous
(cylindrically symmetric) Bose-Einstein condensation (BEC) at low temperature
($T \ll T_{\lambda}$). The main result is the dispersion relation for a (first)
sound wave that is obtained by describing the perturbation as a Lagrangian
coordinate. The dispersion curve is in good agreement with the Bogoliubov
phonon spectrum $\omega=c k$, where $k=k_{\theta}=m/r$, the wave number and
$c=[4 \pi a \rho \hbar^{2}]^{1/2}/M$, the speed of first sound. Based on Bohm's
quantum theory, a spontaneously broken gauge symmetry in a quantum fluid is
discussed in terms of the quantum fluctuation-dissipation, from which it is
shown that the symmetry breaking takes place at the free surface of BEC in an
external field.

20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg