Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Implosion of quadrupole gravitational waves   Einstein's vacuum equations are solved up to the second approximation for
imploding quadrupole gravitational waves. The implosion generates a black hole
singularity irrespective of the strength of the waves.

20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con