English

Distinguishing 4-dimensional geometries via profinite completions

Geometric Topology 2021-01-05 v2

Abstract

It is well-known that there are 19 classes of geometries for 4-dimensional manifolds in the sense of Thurston. We could ask that to what extent the geometric information is revealed by the profinite completion of the fundamental group of a closed smooth geometric 4-manifold. In this paper, we show that the geometry of a closed orientable 4-manifold in the sense of Thurston could be detected by the profinite completion of its fundamental group except when the geometry is H4 \mathbb{H}^{4}, HC2\mathbb{H}^{2}_{\mathbb{C}} or H2×H2\mathbb{H}^2 \times \mathbb{H}^2. Moreover, despite the fact that not every smooth 4-manifold could admit one geometry in the sense of Thurston, some 4-dimensional manifolds with Seifert fibred structures are indeed geometric. For a closed orientable Seifert fibred 4-manifold MM, we show that whether MM is geometric could be detected by the profinite completion of its fundamental group.

Keywords

Cite

@article{arxiv.2011.03784,
  title  = {Distinguishing 4-dimensional geometries via profinite completions},
  author = {Jiming Ma and Zixi Wang},
  journal= {arXiv preprint arXiv:2011.03784},
  year   = {2021}
}