Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Instantons in Schwinger Model   The known calculations of the fermion condensate $<\bar{\psi}\psi>$ and the
correlator $<\bar{\psi}\psi(x) ~\bar{\psi}\psi(0)>$ have been interpreted in
terms of {\em localized} instanton solutions minimizing the {\em effective}
action. Their size is of order of massive photon Compton wavelength $\mu^{-1}$.
At high temperature, these instantons become quasistatic and present the
2-dimensional analog of the `walls' found recently in 4-dimensional gauge
theories. In spite of the static nature of these solutions, they should not be
interpreted as `thermal solitons' living in Minkowski space: the mass of these
would-be solitons does not display itself in the physical correlators. At small
but nonzero fermion mass, the high-T partition function of $QED_2$ is saturated
by the rarefied gas of instantons and antiinstantons with density $\propto
m~\exp\{-S^{inst.}\}~=~m~\exp\{-\pi T/\mu\}$ to be confronted with the dense
strongly correlated instanton-antiinstanton liquid saturating the partition
function at $T=0$.

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The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
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The categories of this paper are: funct-an
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys