Beyond ECH capacities

TL;DR

This paper develops refined ECH-based obstructions to symplectic embeddings, especially for polydisks and convex toric domains, improving upon previous sharpness limitations and proving new embedding restrictions.

Contribution

It introduces enhanced ECH obstructions for convex toric domains, extending symplectic embedding constraints beyond known sharp cases, and proves a conjecture of Schlenk in four dimensions.

Findings

Reproved Hind-Lisi's result on polydisk to ball embeddings

Generalized obstructions to polydisk to ellipsoid embeddings

Proved the four-dimensional case of Schlenk's conjecture

Abstract

ECH (embedded contact homology) capacities give obstructions to symplectically embedding one four-dimensional symplectic manifold with boundary into another. These obstructions are known to be sharp when the domain and target are ellipsoids (proved by McDuff), and more generally when the domain is a "concave toric domain" and the target is a "convex toric domain" (proved by Cristofaro-Gardiner). However ECH capacities often do not give sharp obstructions, for example in many cases when the domain is a polydisk. This paper uses more refined information from ECH to give stronger symplectic embedding obstructions when the domain is a polydisk, or more generally a convex toric domain. We use these new obstructions to reprove a result of Hind-Lisi on symplectic embeddings of a polydisk into a ball, and generalize this to obstruct some symplectic embeddings of a polydisk into an ellipsoid. We also obtain a new obstruction to symplectically embedding one polydisk into another, in particular proving the four-dimensional case of a conjecture of Schlenk.