Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 4-pole analysis of the two-dimensional Hubbard model   The electronic states of the two-dimensional Hubbard model are investigated
by means of a 4-pole approximation within the Composite Operator Method. In
addition to the conventional Hubbard operators, we consider other two
operators, which come from the hierarchy of the equations of motion. These
operators carry information regarding surrounding spin and charge
configurations. By means of this operatorial basis, we can study the physics
related to the energy scale J=4t^2/U. Results present, in addition to the main
two bands, a quasi-particle peak at the Fermi level, shadow bands and band
flatness at (pi, 0) point.

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The categories of this paper are: q-bio
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The categories of this paper are: eess
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
2
The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph