Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological Features of the Magnetic Response in Inhomogeneous Magnetic
  Fields   We present topological features of the magnetic response (orbital and spin)
of a two-dimensional degenerate and non interacting electron gas due to
inhomogeneous applied magnetic fields. These issues are analysed from the point
of view of the Index theory with a special emphasis on the non perturbative
aspects of this response. The limiting case of a Aharonov-Bohm magnetic flux
line is studied in details and the results are extended to more general
situations.

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The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol