Paper detail

Gromov-Witten invariants of $\mathbb{P}^1$ coupled to a KdV tau function

We consider the pull-back of a natural sequence of cohomology classes $Θ_{g,n}\in H^{2(2g-2+n)}(\overline{\cal M}_{g,n})$ to the moduli space of stable maps ${\cal M}^g_n(\mathbb{P}^1,d)$. These classes are related to the Brézin-Gross-Witten tau function of the KdV hierarchy via $Z^{BGW}(\hbar,t_0,t_1,...)=\exp\sum\frac{\hbar^{2g-2}}{n!}\int_{\overline{\cal M}_{g,n}}Θ_{g,n}\cdot\prod_{j=1}^nψ_j^{k_j}\prod t_{k_j}$. Insertions of the pull-backs of the classes $Θ_{g,n}$ into the integrals defining Gromov-Witten invariants define new invariants which we show in the case of target $\mathbb{P}^1$ are given by a random matrix integral and satisfy the Toda equation.