Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Breakdown of the Onsager reaction field theory in two dimensions   It is shown that for the spin 1/2 anisotropic Heisenberg model the result for
the transition temperature is completely insensitive to the anisotropy within
the Onsager reaction field theory, which yields a vanishing T_c in two
dimensions, in total conflict with the expected finite T_c, increasing with
anisotropy. This establishes that the breakdown of the Onsager reaction field
theory in two dimensions is not limited to the Ising model, but actually
extends over the whole range of anisotropy. Therefore, for the isotropic case,
the results of vanishing T_c and exponential dependence of spin correlation
length should be seen as mere coincidence.

18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
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The categories of this paper are: eess
5
The categories of this paper are: gr-qc
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The categories of this paper are: stat
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org