Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orbital Compass Model as an Itinerant Electron System   Two-dimensional orbital compass model is studied as an interacting itinerant
electron model. A Hubbard-type tight-binding model, from which the orbital
compass model is derived in the strong coupling limit, is identified. This
model is analyzed by the random-phase approximation (RPA) and the
self-consistent RPA methods from the weak coupling. Anisotropy for the orbital
fluctuation in the momentum space is qualitatively changed by the on-site
Coulomb interaction. This result is explained by the fact that the dominant
fluctuation is changed from the intra-band nesting to the inter-band one by
increasing the interaction.

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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: nlin