Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Critical point of the two-dimensional Bose gas: an S-matrix approach   A new treatment of the critical point of the two-dimensional interacting Bose
gas is presented. In the lowest order approximation we obtain the critical
temperature T_c ~ 2 \pi n/[ m \log (2\pi/mg)], where n is the density, m the
mass, and g the coupling. This result is based on a new formulation of
interacting gases at finite density and temperature which is reminiscent of the
thermodynamic Bethe ansatz in one dimension. In this formalism, the basic
thermodynamic quantities are expressed in terms of a pseudo-energy. Consistent
resummation of 2-body scattering leads to an integral equation for the
pseudo-energy with a kernel based on the logarithm of the exact 2-body
S-matrix.

32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat