Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-Dimensional Instantons with Bosonization and Physics of Adjoint
  $QCD_2$   We evaluate partition functions $Z_I$ in topologically nontrivial (instanton)
gauge sectors in the bosonized version of the Schwinger model and in a gauged
WZNW model corresponding to $QCD_2$ with adjoint fermions. We show that the
bosonized model is equivalent to the fermion model only if a particular form of
the WZNW action with gauge-invariant integrand is chosen. For the exact
correspondence, it is necessary to integrate over the ways the gauge group
$SU(N)/Z_N$ is embedded into the full $O(N^2 - 1)$ group for the bosonized
matter field. For even $N$, one should also take into account the contributions
of both disconnected components in $O(N^2 - 1)$. In that case, $Z_I \propto
m^{n_0}$ for small fermion masses where $2n_0$ coincides with the number of
fermion zero modes in a particular instanton background. The Taylor expansion
of $Z_I/m^{n_0}$ in mass involves only even powers of $m$ as it should. The
physics of adjoint $QCD_2$ is discussed. We argue that, for odd $N$, the
discrete chiral symmetry $Z_2 \otimes Z_2$ present in the action is broken
spontaneously down to $Z_2$ and the fermion condensate $<\bar{\lambda}
\lambda>_0$ is formed. The system undergoes a first order phase transition at
$T_c = 0$ so that the condensate is zero at an arbitrary small temperature. It
is not yet quite clear what happens for even $N \geq 4$.

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The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
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The categories of this paper are: eess
10
The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
18
The categories of this paper are: econ