Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Asymptotic structure of spacetime and the Newman-Penrose formalism: a
  brief review
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn