Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Tuning the valence and concentration of europium and luminescence
  centers in GaN through co-doping and defect association
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci