Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Terahertz Generation and Amplification in Graphene Nanoribbons in
  Multi-frequency Electric Fields
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th