Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evaluation of the two-particle propagator for Hubbard model with the
  help of Hubbard-I approximation   The Hubbard-I approximation is generalized to allow for direct evaluation of
the equal-time anomalous two-electron propagator for Hubbard model on
two-dimensional square lattice. This propagator is compared against the quantum
Monte Carlo data obtained by Aimi and Imada [J. Phys. Soc. Jpn. {\bf 76},
113708 (2007)] in the limit of strong electron-electron interaction. The
Hubbard-I predictions are in a good qualitative agreement with the Monte Carlo
results. In particular, $d$-wave correlations decay as $c r^{-3}$ ("free
electron" behaviour), if separation $r$ exceeds 2-3 lattice constants. However,
the Hubbard-I approximation underestimates coefficient $c$ by a factor of about
three. We conclude that the Hubbard-I approximation, despite its simplicity and
artefacts, captures the qualitative behaviour of the two-particle propagator
for the Hubbard model, at least for moderate values of $r$.

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The categories of this paper are: eess
29
The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph