Mirror Counts of Spectral Curves

Abstract

Given a convex lattice polygon $\Delta \subset {\mathbb{R}}^2$, let $N_{\Delta }$ be the count of rational, nodal curves in the linear system of the ample line bundle $L_{\Delta }$ on the toric variety ${\mathbb{P}}_{\Delta }$ defined by $\Delta$, having fixed intersection with the toric boundary. We show that the relative Jacobian of the linear system defines an integrable system that has a mirror dual in the language of constructible sheaves on a two-torus microsupported on a Legendrian link. In this setting, we define the dual counting problem using an analogue of rulings of Legendrian links in three-space, then prove equivalence with $N_{\Delta }$. We perform calculations of $N_{\Delta }$ in several examples using constructible methods, tropical curve counting, and localization in logarithmic Gromov-Witten theory to demonstrate the equality of the different approaches. Moreover, the rulings give rise to a stratification of the moduli of constructible sheaves. We conjecture that this ruling decomposition recovers the refined tropical invariants of Block-Göttsche, and hence encodes higher-genus logarithmic Gromov--Witten invariants, by a theorem of Bousseau.

69 pages, 22 figures