Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase transition in ultrathin magnetic films with long range
  interactions   Ultrathin magnetic films can be modeled as an anisotropic Heisenberg model
with long range dipolar interactions. It is believed that the phase diagram
presents three phases: A ordered ferromagnetic phase (I), a phase characterized
by a change from out-of-plane to in-plane in the magnetization (II), and a high
temperature paramagnetic phase (III). It is claimed that the border lines from
phase I to III and II to III are of second order and from I to II is first
order. In the present work we have performed a very careful Monte Carlo
simulation of the model. Our results strongly support that the line separating
phase II and III is of the BKT type.

15
The categories of this paper are: nucl-ex
14
The categories of this paper are: math-ph
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom