Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Black hole hair: twenty--five years after   Originally regarded as forbidden, black hole ``hair'' are fields associated
with a stationary black hole apart from the gravitational and electromagnetic
ones. Several stable stationary black hole solutions with gauge or Skyrme field
hair are known today within general relativity. We formulate here a ``no
scalar--hair'' conjecture, and adduce some new theorems that almost establish
it by ruling out - for all but a small parameter range - scalar field hair of
spherical black holes in general relativity, whether the field be
self--interacting, coupled to an Abelian gauge field, or nonminimally coupled
to gravity.

31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys