Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the electromagnetic field of a charged collapsing spherical shell in
  general relativity   A new exact solution of the Einstein-Maxwell equations for the gravitational
collapse of a shell of matter in an already formed black hole is given. Both
the shell and the black hole are endowed with electromagnetic structure and are
assumed spherically symmetric. Implications for current research are outlined.

25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom