Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Particle approximation of the two-fluid model for superfluid $^4$He
  using smoothed particle hydrodynamics
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
1
The categories of this paper are: cs
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg