Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: MAXI J1820+070 with NuSTAR I. An increase in variability frequency but a
  stable reflection spectrum: coronal properties and implications for the inner
  disc in black hole binaries
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess