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On lens spaces bounding smooth $4$-manifolds with $b_2=1$

Woohyeok Jo, Jongil Park and Kyungbae Park

Algebraic & Geometric Topology 26 (2026) 2659–2688
Abstract

We study which lens spaces can bound smooth 4-manifolds with second Betti number one under various topological conditions. Specifically, we show that there are infinite families of lens spaces that bound compact simply connected smooth 4-manifolds with second Betti number one, yet cannot bound a 4-manifold consisting of a single 0-handle and 2-handle. Additionally, we establish the existence of infinite families of lens spaces that bound compact smooth 4-manifolds with first Betti number zero and second Betti number one, but cannot bound simply connected 4-manifolds with second Betti number one. The construction of such 4-manifolds with lens space boundaries is motivated by the study of rational homology projective planes with cyclic quotient singularities.

Keywords
lens spaces, Donaldson's diagonalization theorem, rational homology projective planes
Mathematical Subject Classification
Primary: 14J17, 57K30, 57K41
References
Publication
Received: 16 February 2025
Revised: 9 September 2025
Accepted: 9 October 2025
Published: 1 September 2026
Authors
Woohyeok Jo
Department of Mathematical Sciences
Seoul National University
Seoul
South Korea
Jongil Park
Department of Mathematical Sciences
Seoul National University
Seoul
South Korea
Kyungbae Park
Department of Mathematics
Kangwon National University
Gangwon
South Korea

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