Mathematical Research Letters

Volume 26 (2019)

Number 2

Trisections of $4$-manifolds via Lefschetz fibrations

Pages: 383 – 420



Nickolas A. Castro (Department of Mathematical Sciences, University of Arkansas, Fayetteville, Ar., U.S.A.)

Burak Ozbagci (Department of Mathematics, University of California at Los Angeles; and Department of Mathematics, Koç University, Istanbul, Turkey)


We develop a technique for gluing relative trisection diagrams of $4$-manifolds with nonempty connected boundary to obtain trisection diagrams for closed $4$-manifolds. As an application, we describe a trisection of any closed $4$-manifold which admits a Lefschetz fibration over $S^2$ equipped with a section of square $-1$, by an explicit diagram determined by the vanishing cycles of the Lefschetz fibration. In particular, we obtain a trisection diagram for some simply connected minimal complex surface of general type. As a consequence, we obtain explicit trisection diagrams for a pair of closed $4$-manifolds which are homeomorphic but not diffeomorphic. Moreover, we describe a trisection for any oriented $S^2$-bundle over any closed surface and in particular we draw the corresponding diagrams for $T^2 \times S^2$ and $T^2 \tilde{\times} S^2$ using our gluing technique. Furthermore, we provide an alternate proof of the fundamental result of Gay and Kirby which says that every closed $4$-manifold admits a trisection. The key feature of our proof is that Cerf theory takes a back seat to contact geometry.

The first author was supported by the UC Davis Chancellor’s Postdoctoral Fellowship Program. The second author was partially supported by a BIDEP-2219 research grant of the Scientific and Technological Research Council of Turkey.

Received 1 August 2017

Accepted 22 April 2018

Published 12 August 2019