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Algorithms in $4$-manifold topology

Stefan Bastl, Rhuaidi Burke, Rima Chatterjee, Subhankar Dey, Alison Durst, Stefan Friedl, Daniel Galvin, Alejandro García Rivas, Tobias Hirsch, Cara Hobohm, Chun-Sheng Hsueh, Marc Kegel, Frieda Kern, Shun Ming Samuel Lee, Clara Löh, Naageswaran Manikandan, Léo Mousseau, Lars Munser, Mark Pencovitch, Patrick Perras, Mark Powell, José Pedro Quintanilha, Lisa Schambeck, David Suchodoll, Martin Tancer, Annika Thiele, Paula Truöl, Matthias Uschold, Simona Veselá, Melvin Weiss and Magdalina von Wunsch-Rolshoven

Algebraic & Geometric Topology 26 (2026) 3017–3049
DOI: 10.2140/agt.2026.26.3017
Abstract

We show that there exists an algorithm that takes as input two closed, simply connected, topological 4-manifolds and decides whether or not these 4-manifolds are homeomorphic. In particular, we explain in detail how closed, simply connected, topological 4-manifolds can be naturally represented by a Kirby diagram consisting only of 2-handles. This representation is used as input for our algorithm. Along the way, we develop an algorithm to compute the Kirby–Siebenmann invariant of a closed, simply connected, topological 4-manifold from any of its Kirby diagrams and describe an algorithm that decides whether or not two intersection forms are isometric.

In a slightly different direction, we discuss the decidability of the stable classification of smooth manifolds with more general fundamental groups. Here we show that there exists an algorithm that takes as input two closed, oriented, smooth 4-manifolds with fundamental groups isomorphic to a finite group with cyclic Sylow 2-subgroup, an infinite cyclic group, or a group of geometric dimension at most 3 (in the latter case we additionally assume that the universal covers of both 4-manifolds are not spin), and decides whether or not these two 4-manifolds are orientation-preserving stably diffeomorphic.

Keywords
$4$-manifolds, algorithms
Mathematical Subject Classification
Primary: 57K40
Secondary: 57K10, 57R65
References
Publication
Received: 22 November 2024
Revised: 4 August 2025
Accepted: 6 September 2025
Published: 13 November 2026
Authors
Stefan Bastl
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Rhuaidi Burke
School of Mathematics and Physics
The University of Queensland
Brisbane
Australia
Rima Chatterjee
School of Mathematics and Physics
The University of Queensland
Brisbane
Australia
Subhankar Dey
Department of Mathematics
IIT Palakkad
Palakkad
India
Alison Durst
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Stefan Friedl
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Daniel Galvin
Department of Mathematics
The University of Texas at Austin
Austin, TX
United States
Alejandro García Rivas
Universität Bonn
Bonn
Germany
Tobias Hirsch
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Cara Hobohm
Universität Bonn
Bonn
Germany
Chun-Sheng Hsueh
Humboldt Universität zu Berlin
Berlin
Germany
Marc Kegel
Departamento de Álgebra
Universidad de Sevilla
Sevilla
Spain
Frieda Kern
Universität Bonn
Bonn
Germany
Shun Ming Samuel Lee
Universität Bonn
Bonn
Germany
Clara Löh
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Naageswaran Manikandan
Humboldt Universität zu Berlin
Berlin
Germany
Léo Mousseau
Humboldt Universität zu Berlin
Berlin
Germany
Lars Munser
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Mark Pencovitch
School of Mathematics and Statistics
University of Glasgow
Glasgow
United Kingdom
Patrick Perras
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Mark Powell
School of Mathematics and Statistics
University of Glasgow
Glasgow
United Kingdom
José Pedro Quintanilha
Fakultät für Mathematik und Informatik
Universität Heidelberg
Heidelberg
Germany
Lisa Schambeck
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
David Suchodoll
Humboldt Universität zu Berlin
Berlin
Germany
Martin Tancer
Department of Applied Mathematics
Charles University
Prague
Czech Republic
Annika Thiele
Humboldt Universität zu Berlin
Berlin
Germany
Paula Truöl
Max Planck Institute for Mathematics
Bonn
Germany
Matthias Uschold
Fakultät für Mathematik
Universität Regensburg
Regensburg
Germany
Simona Veselá
Universität Bonn
Bonn
Germany
Melvin Weiss
Universität Bonn
Bonn
Germany
Magdalina von Wunsch-Rolshoven
Universität Bonn
Bonn
Germany

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