Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The two-phase issue in the O(n) non-linear $\sigma$-model: A Monte Carlo
  study   We have performed a high statistics Monte Carlo simulation to investigate
whether the two-dimensional O(n) non-linear sigma models are asymptotically
free or they show a Kosterlitz- Thouless-like phase transition. We have
calculated the mass gap and the magnetic susceptibility in the O(8) model with
standard action and the O(3) model with Symanzik action. Our results for O(8)
support the asymptotic freedom scenario.

4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc