Corpus ID: 235435895

Cartan projections of some nonreductive subgroups and proper actions on homogeneous spaces

@inproceedings{Morita2021CartanPO,
  title={Cartan projections of some nonreductive subgroups and proper actions on homogeneous spaces},
  author={Yosuke Morita},
  year={2021}
}
Kobayashi [Duke Math. J. (1992)] gave a necessary condition for the existence of compact Clifford–Klein forms in terms of Cartan projections and noncompact dimensions of reductive subgroups. We extend his method to nonreductive subgroups, and give some examples of homogeneous spaces of reductive type that do not admit compact Clifford–Klein forms by comparing Cartan projections and noncompact dimensions of reductive subgroups with those of nonreductive subgroups. 

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