Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-perturbative gauge transformations of arbitrary fermion correlation
  functions in quantum electrodynamics   We study the transformation of the dressed electron propagator and the
general $N$-point functions under a change in the covariant gauge of internal
photon propagators. We re-establish the well known Landau-Khalatnikov-Fradkin
transformation for the propagator and generalise it to arbitrary correlation
functions in configuration space, finding that it coincides with the analogous
result for scalar fields. We comment on the consequences for perturbative
application in momentum-space.

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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: nlin