Diffeotopy groups of non-compact 4-manifolds

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1. Verfasser: Nonino, Isacco
Format: Preprint
Veröffentlicht: 2022
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author Nonino, Isacco
author_facet Nonino, Isacco
contents We provide information on diffeotopy groups of exotic smoothings of punctured 4-manifolds, extending previous results on diffeotopy groups of exotic $\mathbb{R}^4$'s. In particular, we prove that for a smoothable 4-manifold $M$ and for a non-empty, discrete set of points $S \subsetneq \mathring{M}$, there are uncountably many distinct smoothings of $M\smallsetminus S$ whose diffeotopy groups are uncountable. We then prove that for a smoothable 4-manifold $M$ and for a non-empty, discrete set of points $S \subsetneq \mathring{M}$, there exists a smoothing of $M\smallsetminus S$ whose diffeotopy groups have similar properties as $\mathcal{R}_U$, Freedman and Taylor's universal $\mathbb{R}^4$. Moreover, we prove that if $M$ is non-smoothable, both results still hold under the assumption that $|S| \ge 2$.
format Preprint
id arxiv_https___arxiv_org_abs_2203_09433
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Diffeotopy groups of non-compact 4-manifolds
Nonino, Isacco
Geometric Topology
57R50, 57S05, 20F38, 57R55, 57K40
We provide information on diffeotopy groups of exotic smoothings of punctured 4-manifolds, extending previous results on diffeotopy groups of exotic $\mathbb{R}^4$'s. In particular, we prove that for a smoothable 4-manifold $M$ and for a non-empty, discrete set of points $S \subsetneq \mathring{M}$, there are uncountably many distinct smoothings of $M\smallsetminus S$ whose diffeotopy groups are uncountable. We then prove that for a smoothable 4-manifold $M$ and for a non-empty, discrete set of points $S \subsetneq \mathring{M}$, there exists a smoothing of $M\smallsetminus S$ whose diffeotopy groups have similar properties as $\mathcal{R}_U$, Freedman and Taylor's universal $\mathbb{R}^4$. Moreover, we prove that if $M$ is non-smoothable, both results still hold under the assumption that $|S| \ge 2$.
title Diffeotopy groups of non-compact 4-manifolds
topic Geometric Topology
57R50, 57S05, 20F38, 57R55, 57K40
url https://arxiv.org/abs/2203.09433