Stein trisections and homotopy 4-balls

TL;DR

This paper introduces a new construction for homotopy 4-balls in complex 2-space, providing conditions under which such balls are shown to be standard, advancing understanding of the smooth 4-dimensional Schoenflies problem.

Contribution

It presents a reimbedding method for homotopy 4-balls in ^2 and offers an analytic criterion for identifying when these are standard 4-balls.

Findings

Constructed a diffeomorphic domain as a union of three pseudoconvex domains.

Provided an analytic criterion for a homotopy 4-ball to be standard.

Enhanced understanding of the smooth 4-dimensional Schoenflies problem.

Abstract

A homotopy 4-ball is a smooth 4-manifold with boundary $S^3$ that is homotopy-equivalent to the standard $B^4$. The smooth 4-dimensional Schoenflies problem asks whether every homotopy 4-ball in $S^4$ (or equivalently $\mathbb{C}^2$) is standard. It is well-known that if a homotopy 4-ball embeds as a compact, pseudoconvex domain in a Stein surface, then it must be standard. In this paper, we describe a compelling reimbedding construction for homotopy 4-balls in $\mathbb{C}^2$. In particular, given a homotopy 4-ball in $\mathbb{C}^2$, we construct a diffeomorphic domain that is the union of three pseudoconvex domains. Moreover, we give an analytic criterion that ensures this domain is a standard 4-ball.