Trisecting Smooth 4-dimensional Cobordisms

TL;DR

This paper generalizes the theory of relative trisections for 4-manifolds with boundary, allowing for multiple boundary components and providing conditions for gluing, thereby creating a categorical framework for trisected cobordisms.

Contribution

It extends the theory of relative trisections to include multiple boundary components and establishes conditions for gluing, forming a new categorical structure for 4-manifolds.

Findings

Extended relative trisections to 4-manifolds with multiple boundary components.

Provided conditions for gluing trisected 4-manifolds along boundary components.

Defined a category of trisected cobordisms with open book decompositions.

Abstract

We extend the theory of relative trisections of smooth, compact, oriented $4$-manifolds with connected boundary given by Gay and Kirby to include $4$-manifolds with an arbitrary number of boundary components. Additionally, we provide sufficient conditions under which relatively trisected $4$-manifolds can be glued to one another along diffeomorphic boundary components so as to induce a trisected manifold. These two results allow us to define a category $\textrm{Tri}$ whose objects are smooth, closed, oriented $3$-manifolds equipped with open book decompositions, and morphisms are relatively trisected cobordisms. Additionally, we extend the Hopf stabilization of open book decompositions to a relative stabilization of relative trisections.