Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Finite Size Effects and Conformal Symmetry of $O(N)$ Nonlinear $\sigma$
  Model in Three Dimensions   We study the $O(N)$ nonlinear $\sigma$ model on a three-dimensional compact
space $S^1 \times S^2$ (of radii $L$ and $R$ respectively) by means of large
$N$ expansion, focusing on the finite size effects and conformal symmetries of
this model at the critical point. We evaluate the correlation length and the
Casimir energy of this model and study their dependence on $L$ and $R$. We
examine the modular transformation properties of the partition function, and
study the dependence of the specific heat on the mass gap in view of possible
extension of the $C-$theorem to three dimensions.

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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: plasm-ph
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The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph