Exotic Dehn twists on 4-manifolds

Fuente: arXiv
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Main Authors: Konno, Hokuto, Mallick, Abhishek, Taniguchi, Masaki
Format: Preprint
Published: 2023
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author Konno, Hokuto
Mallick, Abhishek
Taniguchi, Masaki
author_facet Konno, Hokuto
Mallick, Abhishek
Taniguchi, Masaki
contents We initiate the study of exotic Dehn twists along 3-manifolds $\neq S^3$ inside $4$-manifolds, which produces the first known examples of exotic diffeomorphisms of contractible 4-manifolds, more generally of definite 4-manifolds, and exotic diffeomorphisms of 4-manifolds with $\neq S^3$ boundary that survive after one stabilization. We also construct the smallest closed 4-manifold known to support an exotic diffeomorphism. These exotic diffeomorphisms are the Dehn twists along certain Seifert fibered 3-manifolds. As a consequence, we get loops of diffeomorphisms of 3-manifolds that topologically extend to some 4-manifolds $X$ but not smoothly so, implying the non-surjectivity of $π_1(\mathrm{Diff}(X)) \to π_1(\mathrm{Homeo}(X))$. Our method uses $2$-parameter families Seiberg-Witten theory over $\mathbb{RP}^2$, while known methods to detect exotic diffeomorphisms used $1$-parameter families gauge-theoretic invariants. Using a similar strategy, we construct a new kind of exotic diffeomorphisms of 4-manifolds, given as commutators of diffeomorphisms.
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id arxiv_https___arxiv_org_abs_2306_08607
institution arXiv
publishDate 2023
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spellingShingle Exotic Dehn twists on 4-manifolds
Konno, Hokuto
Mallick, Abhishek
Taniguchi, Masaki
Geometric Topology
Differential Geometry
We initiate the study of exotic Dehn twists along 3-manifolds $\neq S^3$ inside $4$-manifolds, which produces the first known examples of exotic diffeomorphisms of contractible 4-manifolds, more generally of definite 4-manifolds, and exotic diffeomorphisms of 4-manifolds with $\neq S^3$ boundary that survive after one stabilization. We also construct the smallest closed 4-manifold known to support an exotic diffeomorphism. These exotic diffeomorphisms are the Dehn twists along certain Seifert fibered 3-manifolds. As a consequence, we get loops of diffeomorphisms of 3-manifolds that topologically extend to some 4-manifolds $X$ but not smoothly so, implying the non-surjectivity of $π_1(\mathrm{Diff}(X)) \to π_1(\mathrm{Homeo}(X))$. Our method uses $2$-parameter families Seiberg-Witten theory over $\mathbb{RP}^2$, while known methods to detect exotic diffeomorphisms used $1$-parameter families gauge-theoretic invariants. Using a similar strategy, we construct a new kind of exotic diffeomorphisms of 4-manifolds, given as commutators of diffeomorphisms.
title Exotic Dehn twists on 4-manifolds
topic Geometric Topology
Differential Geometry
url https://arxiv.org/abs/2306.08607