Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ground state energy of the two-dimensional weakly interacting Bose gas:
  First correction beyond Bogoliubov theory   We consider the grand potential $\Omega$ of a two-dimensional weakly
interacting homogeneous Bose gas at zero temperature. Building on a
number-conserving Bogoliubov method for a lattice model in the grand canonical
ensemble, we calculate the next order term as compared to the Bogoliubov
prediction, in a systematic expansion of $\Omega$ in powers of the parameter
measuring the weakness of the interaction. Our prediction is in very good
agreement with recent Monte Carlo calculations.

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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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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: eess
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex