Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Probing the nature of compact dark object at the Galactic Center by
  gravitational lensing
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph