Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On chiral symmetry breaking by external magnetic fields in QED$_3$   A recent result of Gusynin, Miransky and Shovkovy concerning chiral symmetry
breaking by a constant external magnetic field in parity-invariant
three-dimensional QED is generalised to the case of inhomogeneous fields by
relating the phenomenon to the zero modes of the Dirac equation. Virtual photon
radiative corrections and four-dimensional QED are briefly discussed.

15
The categories of this paper are: nucl-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th