English

A nonstandard construction of direct limit group actions

Group Theory 2022-04-18 v3

Abstract

Manevitz and Weinberger (1996) proved that the existence of effective KK-Lipschitz Z/nZ\mathbb{Z}/n\mathbb{Z}-actions implies the existence of effective KK-Lipschitz Q/Z\mathbb{Q}/\mathbb{Z}-actions for all compact connected manifolds with metrics, where KK is a fixed Lipschitz constant. The Q/Z\mathbb{Q}/\mathbb{Z}-actions were constructed from suitable actions of a sufficiently large hyperfinite cyclic group Z/γZ{}^{\ast}{\mathbb{Z}}/\gamma{}^{\ast}{\mathbb{Z}} in the sense of nonstandard analysis. By modifying their construction, we prove that for every direct system (Λ,Gλ,iλμ)\left(\Lambda,G_{\lambda},i_{\lambda\mu}\right) of torsion groups with monomorphisms, the existence of effective KK-Lipschitz GλG_{\lambda}-actions implies the existence of effective KK-Lipschitz limGλ\varinjlim G_{\lambda}-actions. This generalises Manevitz and Weinberger's result.

Keywords

Cite

@article{arxiv.1812.00575,
  title  = {A nonstandard construction of direct limit group actions},
  author = {Takuma Imamura},
  journal= {arXiv preprint arXiv:1812.00575},
  year   = {2022}
}