Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum theory of the third-order nonlinear electrodynamic effects in
  graphene   The linear energy dispersion of graphene electrons leads to a strongly
nonlinear electromagnetic response of this material. We develop a general
quantum theory of the third-order nonlinear local dynamic conductivity of
graphene $\sigma_{\alpha\beta\gamma\delta}(\omega_1,\omega_2,\omega_3)$, which
describes its nonlinear response to a uniform electromagnetic radiation. The
derived analytical formulas describe a large number of different nonlinear
phenomena such as the third harmonic generation, the four wave mixing, the
saturable absorption, the second harmonic generation stimulated by a dc
electric current, etc., which may be used in different terahertz and
optoelectronic devices.

2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga