Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nuts have no hair   We show that the Riemannian Kerr solutions are the only Riemannian,
Ricci-flat and asymptotically flat ${\rm C}^{2}$-metrics $g_{\mu\nu}$ on a
4-dimensional complete manifold ${\cal M}$ of topology ${\rm R}^{2} \times {\rm
S}^{2}$ which have (at least) a 1-parameter group of periodic isometries with
only isolated fixed points ("nuts") and with orbits of bounded length at
infinity.

34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs