Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Order-Disorder Transition in the Two-Dimensional Spatially
  Anisotropic Heisenberg Model at Zero Temperature   The ground-state properties of the spin-1/2 antiferromagnetic Heisenberg
model with spatially anisotropic couplings on a square lattice are investigated
by a spin-rotation-invariant Green's-function approach and by Lanczos
diagonalizations on lattices up to 36 sites supplemented by finite-size
scaling. We focus on the anisotropy-driven transition from the N\'eel state to
a paramagnetic state with antiferromagnetic short-range order and on the
spatial dependence of spin correlation functions. Our principal result is that
a rather sharp crossover in the magnetic behavior occurs at the coupling ratio
$R_0\simeq 0.2$ ($R=J_y/J_x$).

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The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: funct-an