Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Euclidean two-point correlation function of the topological charge
  density   We study the Euclidean two-point correlation function $G_q(x)$ of the
topological charge density in QCD. A general statement based on reflection
positivity tells us that $G_q(x)<0$ for $x\neq 0 $. On the other hand the
topological susceptibility $\chi_q=\int d^d x G_q(x)$ is a positive quantity.
This indicates that $G_q(x)$ developes a positive contact term at $x=0$, that
contributes to the determination of the physical value of $\chi_q$. We show
explicitly these features of $G_q(x)$ in a solvable nontrivial continuum model,
the two-dimensional $CP^{N-1}$ model in the large-N limit. A similar analysis
is done on the lattice.

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The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
1
The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: chao-dyn