Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An intrinsic characterization of the Kerr metric   We give the necessary and sufficient (local) conditions for a metric tensor
to be the Kerr solution. These conditions exclusively involve explicit
concomitants of the Riemann tensor.

27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics