Journal of Symplectic Geometry

Volume 18 (2020)

Number 3

A new approach to the symplectic isotopy problem

Pages: 939 – 960



Laura Starkston (Department of Mathematics, University of California at Davis)


The symplectic isotopy conjecture states that every smooth symplectic surface in $\mathbb{C}\mathrm{P}^2$ is symplectically isotopic to a complex algebraic curve. Progress began with Gromov’s pseudoholomorphic curves [Gro85], and progressed further culminating in Siebert and Tian’s proof of the conjecture up to degree $17$ [ST05], but further progress has stalled. In this article we provide a new direction of attack on this problem. Using a solution to a nodal symplectic isotopy problem we guide model symplectic isotopies of smooth surfaces. This results in an equivalence between the smooth symplectic isotopy problem and an existence problem of certain embedded Lagrangian disks. This redirects study of this problem from the realm of pseudoholomorphic curves of high genus to the realm of Lagrangians and Floer theory. Because the main theorem is an equivalence going both directions, it could theoretically be used to either prove or disprove the symplectic isotopy conjecture.

Received 14 November 2017

Accepted 16 July 2019

Published 30 July 2020