Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Constraints on the mean free path of ionising photons at $z\sim6$ using
  limits on individual free paths
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci