English

When actions of amenable groups can be lifted to the universal cover

Geometric Topology 2015-07-20 v4 Dynamical Systems

Abstract

In the first part of this paper, we let GG be a finitely-generated amenable group such that G/[G,G]G/[G, G] is torsion-free. We suppose that GG acts by homeomorphisms homotopic to the identity on a manifold MM, and give conditions on MM which imply that such an action must lift to an action on the universal cover M~\tilde{M}. The circle, all 2-manifolds except the open annulus, and most compact 3-manifolds satisfy these conditions. The proof uses a dynamical tool called homological rotation vectors, and Thurston's Geometrization Theorem in the latter case. On manifolds not satisfying our conditions, such actions really may fail to lift. In the second part, we try to understand the dynamical possibilities in the simplest case: G=Z2G = \mathbb{Z}^2, and M=AM = \mathbb{A} is the open annulus. We show that if a Z2\mathbb{Z}^2 action homotopic to the identity on A\mathbb{A} fails to lift to a Z2\mathbb{Z}^2 action on the plane, and if the action satisfies one additional condition (which may not be necessary), the action is essentially similar to the one generated by f0ˉ(θ,y)=(θ+y,y)\bar{f_0}(\theta, y) = (\theta + y, y) and g0ˉ(θ,y)=(θ,y+1)\bar{g_0}(\theta, y) = (\theta, y + 1).

Keywords

Cite

@article{arxiv.1409.6422,
  title  = {When actions of amenable groups can be lifted to the universal cover},
  author = {Kiran Parkhe},
  journal= {arXiv preprint arXiv:1409.6422},
  year   = {2015}
}

Comments

26 pages, 1 figure