On the Open TS/ST Correspondence

Abstract The topological string/spectral theory correspondence establishes a precise, non-perturbative duality between topological strings on local Calabi-Yau threefolds and the spectral theory of quantized mirror curves. While this duality has been rigorously formulated for the closed topological string sector, the open string sector remains less understood. Building on the results of Marino and Zakany (J Phys A 50:325401, 2017. https://doi.org/10.1088/1751-8121/aa791e , JHEP 05:014, 2019. https://doi.org/10.1007/JHEP05(2019)014 ) and François and Grassi (Ann Henri Poincaré 26:2117, 2025. https://doi.org/10.1007/s00023-024-01469-4 ), we make further progress in this direction by constructing entire, off-shell eigenfunctions for the quantized mirror curve from open topological string partition functions. We focus on local $$\mathbb {F}_0$$ F 0 , whose mirror curve corresponds to the Baxter equation of the two-particle, relativistic Toda lattice. We then study the standard and dual four-dimensional limits, where the quantum mirror curve for local $$\mathbb {F}_0$$ F 0 degenerates into the modified Mathieu and McCoy–Tracy–Wu operators, respectively. In these limits, our framework provides a way to construct entire, off-shell eigenfunctions for the difference equations associated with these operators. Furthermore, we find a simple relation between the on-shell eigenfunctions of the modified Mathieu and McCoy–Tracy–Wu operator, leading to a functional relation between the operators themselves.