Constraints on Lefschetz fibrations with four-dimensional fibers from Seiberg-Witten theory

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Autori principali: Konno, Hokuto, Lin, Jianfeng, Mukherjee, Anubhav, Muñoz-Echániz, Juan
Natura: Preprint
Pubblicazione: 2025
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author Konno, Hokuto
Lin, Jianfeng
Mukherjee, Anubhav
Muñoz-Echániz, Juan
author_facet Konno, Hokuto
Lin, Jianfeng
Mukherjee, Anubhav
Muñoz-Echániz, Juan
contents We establish constraints on the topology of smooth Lefschetz fibrations with $4$-dimensional fibers, by studying the family Bauer-Furuta invariant. To compute this invariant, we analyze the framed bordism class of 1-dimensional Seiberg-Witten moduli spaces using the local index theorem by Bismut-Freed. Using this, we deduce new obstructions to the smooth isotopy to the identity for compositions of Dehn twists on $(-2)$-spheres in closed $4$-manifolds. We obtain several applications: (1) We exhibit the first examples of closed simply-connected symplectic $4$-manifolds admitting Torelli symplectomorphisms which are smoothly non-trivial. In particular, their symplectic Torelli mapping class group is not generated by squared Dehn-Seidel twists on Lagrangian spheres -- providing a negative answer to a question of Donaldson. (2) We provide the first examples of irreducible closed $4$-manifolds (both symplectic and non-symplectic) that admit exotic diffeomorphisms given by Seifert-fibered Dehn twist.
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id arxiv_https___arxiv_org_abs_2511_00601
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Constraints on Lefschetz fibrations with four-dimensional fibers from Seiberg-Witten theory
Konno, Hokuto
Lin, Jianfeng
Mukherjee, Anubhav
Muñoz-Echániz, Juan
Geometric Topology
Algebraic Geometry
Differential Geometry
Symplectic Geometry
We establish constraints on the topology of smooth Lefschetz fibrations with $4$-dimensional fibers, by studying the family Bauer-Furuta invariant. To compute this invariant, we analyze the framed bordism class of 1-dimensional Seiberg-Witten moduli spaces using the local index theorem by Bismut-Freed. Using this, we deduce new obstructions to the smooth isotopy to the identity for compositions of Dehn twists on $(-2)$-spheres in closed $4$-manifolds. We obtain several applications: (1) We exhibit the first examples of closed simply-connected symplectic $4$-manifolds admitting Torelli symplectomorphisms which are smoothly non-trivial. In particular, their symplectic Torelli mapping class group is not generated by squared Dehn-Seidel twists on Lagrangian spheres -- providing a negative answer to a question of Donaldson. (2) We provide the first examples of irreducible closed $4$-manifolds (both symplectic and non-symplectic) that admit exotic diffeomorphisms given by Seifert-fibered Dehn twist.
title Constraints on Lefschetz fibrations with four-dimensional fibers from Seiberg-Witten theory
topic Geometric Topology
Algebraic Geometry
Differential Geometry
Symplectic Geometry
url https://arxiv.org/abs/2511.00601