Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic-field quantization and spontaneous decay in left-handed
  media   We present a quantization scheme for the electromagnetic field interacting
with atomic systems in the presence of dispersing and absorbing
magnetodielectric media, including left-handed material having negative real
part of the refractive index. The theory is applied to the spontaneous decay of
a two-level atom at the center of a spherical free-space cavity surrounded by
magnetodielectric matter of overlapping band-gap zones. Results for both big
and small cavities are presented, and the problem of local-field corrections
within the real-cavity model is addressed.

36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat