Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Berezinskii-Kosterlitz-Thouless transition in two-dimensional lattice
  gas models   We have considered two classical lattice-gas models, consisting of particles
that carry multicomponent magnetic momenta, and associated with a
two-dimensional square lattices; each site can host one particle at most, thus
implicitly allowing for hard-core repulsion; the pair interaction, restricted
to nearest neighbors, is ferromagnetic and involves only two components. The
case of zero chemical potential has been investigated by Grand--Canonical Monte
Carlo simulations; the fluctuating occupation numbers now give rise to
additional fluid-like observables in comparison with the usual
saturated--lattice situation; these were investigated and their possible
influence on the critical behaviour was discussed. Our results show that the
present model supports a Berezinskii-Kosterlitz-Thouless phase transition with
a transition temperature lower than that of the saturated lattice counterpart
due to the presence of ``vacancies''; comparisons were also made with similar
models studied in the literature.

25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph