Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal Dynamic Conductivity and Quantized Visible Opacity of
  Suspended Graphene   We show that the optical transparency of suspended graphene is defined by the
fine structure constant, alpha, the parameter that describes coupling between
light and relativistic electrons and is traditionally associated with quantum
electrodynamics rather than condensed matter physics. Despite being only one
atom thick, graphene is found to absorb a significant (pi times alpha=2.3%)
fraction of incident white light, which is a consequence of graphene's unique
electronic structure. This value translates into universal dynamic conductivity
G =e^2/4h_bar within a few percent accuracy.

7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics