Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Coherent dynamics of localized excitons and trions in ZnO/(Zn,Mg)O
  quantum wells studied by photon echoes
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex