Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Absence of a Magnetic Phase Transition in Heisenberg, Hubbard, and
  Kondo-lattice (s-f) Films   The possibility of a magnetic phase transition in Heisenberg, Hubbard, and
s-f (Kondo-lattice) films is investigated. It is shown that, for any finite
temperature and any finite number of layers, the magnetization within every
layer must vanish. Thus, the Mermin-Wagner theorem is extended to a variety of
system geometries. We also comment on the microscopic interpretation of the
transition from two to three dimensions in the limit of an infinite number of
layers.

6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat