Elliptic orbifold lines and integrable hierarchies

Abstract

We prove that the Gromov--Witten invariants of the elliptic orbifold lines $\mathbf{P}^1_{3,3,3}$, $\mathbf{P}^1_{2,4,4}$, and $\mathbf{P}^1_{2,3,6}$ satisfy a certain system of Hirota Quadratic (or Bilinear) Equations. Our result is the analogue of the so-called Toda conjecture in the Gromov-Witten theory of $\mathbf{P}^1$ or more precisely its non-extended version. A new feature in our constructions is a certain bilinear operator whose principal symbol can be expressed in terms of elliptic theta functions.