Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A topological necessary condition for the existence of compact
  Clifford-Klein forms   We provide a necessary condition for the existence of a compact
Clifford-Klein form of a given homogeneous space of reductive type. The key to
the proof is to combine a result of Kobayashi-Ono with an elementary fact that
certain two different Clifford-Klein forms have the same cohomology ring. We
give some examples, SL(p+q, R)/SO(p, q) (p, q: odd) for instance, of
homogeneous spaces which do not admit compact Clifford-Klein forms.

16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph