Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Photon storage in Lambda-type optically dense atomic media. IV. Optimal
  control using gradient ascent
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th