Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the universal optical conductivity and single-particle relaxation in
  cuprates   The origin of the universal optical conductivity form sigma(omega) ~
(1-e^(omega/T))/omega established in numerical model studies of doped
antiferromagnets and consistent with experiments on cuprates near optimal
doping is discussed. It is shown that such a behaviour appears quite generally
when the single-particle excitations are overdamped and their relaxation
follows the marginal Fermi liquid concept. Relation to recent ARPES experiments
is also discussed.

19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an