Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: QED Effective Action in Magnetic Field Backgrounds and Electromagnetic
  Duality   In the in-out formalism we advance a method of the inverse scattering matrix
for calculating effective actions in pure magnetic field backgrounds. The
one-loop effective actions are found in a localized magnetic field of Sauter
type and approximately in a general magnetic field by applying the uniform
semiclassical approximation. The effective actions exhibit the electromagnetic
duality between a constant electric field and a constant magnetic field and
between $E(x) = E sech^2 (x/L)$ and $B(x) = B sech^2 (x/L)$.

19
The categories of this paper are: eess
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The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
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The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin