Dehn twists and the Nielsen realization problem for spin 4-manifolds

Fuente: arXiv
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Main Author: Konno, Hokuto
Format: Preprint
Published: 2022
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author Konno, Hokuto
author_facet Konno, Hokuto
contents We prove that, for a closed oriented smooth spin 4-manifold $X$ with non-zero signature, the Dehn twist about a $(+2)$- or $(-2)$-sphere in $X$ is not homotopic to any finite order diffeomorphism. In particular, we negatively answer the Nielsen realization problem for each group generated by the mapping class of a Dehn twist. We also show that there is a discrepancy between the Nielsen realization problems in the topological category and smooth category for connected sums of copies of $K3$ and $S^{2} \times S^{2}$. The main ingredients of the proofs are Y. Kato's 10/8-type inequality for involutions and a refinement of it.
format Preprint
id arxiv_https___arxiv_org_abs_2203_11631
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Dehn twists and the Nielsen realization problem for spin 4-manifolds
Konno, Hokuto
Geometric Topology
Differential Geometry
We prove that, for a closed oriented smooth spin 4-manifold $X$ with non-zero signature, the Dehn twist about a $(+2)$- or $(-2)$-sphere in $X$ is not homotopic to any finite order diffeomorphism. In particular, we negatively answer the Nielsen realization problem for each group generated by the mapping class of a Dehn twist. We also show that there is a discrepancy between the Nielsen realization problems in the topological category and smooth category for connected sums of copies of $K3$ and $S^{2} \times S^{2}$. The main ingredients of the proofs are Y. Kato's 10/8-type inequality for involutions and a refinement of it.
title Dehn twists and the Nielsen realization problem for spin 4-manifolds
topic Geometric Topology
Differential Geometry
url https://arxiv.org/abs/2203.11631