English

Almost fixed points of finite group actions on manifolds without odd cohomology

Differential Geometry 2018-05-08 v1 Group Theory Geometric Topology

Abstract

If XX is a smooth manifold and G{\mathcal{G}} is a subgroup of Diff(X)Diff(X) we say that (X,G)(X,{\mathcal{G}}) has the almost fixed point property if there exists a number CC such that for any finite subgroup GGG\leq{\mathcal{G}} there is some xXx\in X whose stabilizer GxGG_x\leq G satisfies [G:Gx]C[G:G_x]\leq C. We say that XX has no odd cohomology if its integral cohomology is torsion free and supported in even degrees. We prove that if XX is compact and possibly with boundary and has no odd cohomology then (X,Diff(X))(X,Diff(X)) has the almost fixed point property. Combining this with a result of Petrie and Randall we conclude that if ZZ is a non necessarily compact smooth real affine variety, and ZZ has no odd cohomology, then (Z,Aut(Z))(Z,Aut(Z)) has the almost fixed point property, where Aut(Z)Aut(Z) is the group of algebraic automorphisms of ZZ lifting the identity on SpecRSpec\,{\mathbb{R}}.

Keywords

Cite

@article{arxiv.1805.02582,
  title  = {Almost fixed points of finite group actions on manifolds without odd cohomology},
  author = {Ignasi Mundet i Riera},
  journal= {arXiv preprint arXiv:1805.02582},
  year   = {2018}
}

Comments

17 pages; This paper is one of the two parts in which arXiv:1403.0383v3 has been split. Most of its contents appeared in arXiv:1310.6565, but the material has been substantially revised. Some results on algebraic actions on smooth real affine varieties have been added