Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin-Peierls Dimerization of a s=1/2 Heisenberg Antiferromagnet on a
  Square Lattice   Dimerization of a spin-half Heisenberg antiferromagnet on a square lattice is
investigated for several possible dimerized configurations, some of which are
shown to have lower ground state energies than the others. In particular, the
lattice deformations resulting in alternate stronger and weaker couplings along
both the principal axes of a square lattice are shown to result in a larger
gain in magnetic energy. In addition, a `columnar' configuration is shown to
have a lower ground state energy and a faster increase in the energy gap
parameter than a `staggered' configuration. The inclusion of unexpanded
exchange coupling leads to a power law behaviour for the magnetic energy gain
and energy gap, which is qualitatively different from that reported earlier.
Instead of increasing as $\delta ^{x}$, the two quantities depend on $\delta $
as $\delta ^{\nu}/| \ln \delta | .$ This is true both in the near critical
regime $(0\leq \delta \leq 0.1)$ as well as in the far regime $(0\leq \delta
<1)$. It is suggested that the unexpanded exchange coupling is as much a source
of the logarithmic dependence as a correction due to the contribution of
umklapp processes. Staggered magnetization is shown to follow the same $\delta
$-dependence in all the configurations in the small $\delta $-regime, while for
$0\leq \delta <1$, it follows the power law $\delta ^{x}$.

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The categories of this paper are: hep-lat
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: chem-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: econ