Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Using 21cm Absorption in Small Impact Parameter Galaxy-QSO Pairs to
  Probe Low-Redshift Damped and Sub-Damped Lyman-alpha System
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org