Quasi-homogeneity of the moduli space of stable maps to homogeneous spaces (II)

Abstract

Let $G$ be a connected, simply connected, simple, complex, linear algebraic group. Let $P$ be an arbitrary parabolic subgroup of $G$. Let $X=G/P$ be the $G$-homogeneous projective space attached to this situation. Let $d\in H_2(X)$ be a degree. Let $\overline{M}_{0,3}(X,d)$ be the (coarse) moduli space of three pointed genus zero stable maps to $X$ of degree $d$. Building on and improving our previous results [Christoph B\"arligea, Quasi-Homogeneity of the Moduli Space of Stable Maps to Homogeneous Spaces, Doc. Math. 23, 697-745 (2018), DOI: 10.25537/dm.2018v23.697-745], we prove that $\overline{M}_{0,3}(X,d)$ is quasi-homogeneous under the action of $\operatorname{Aut}(X)$ for all minimal degrees $d$ in $H_2(X)$. By a minimal degree in $H_2(X)$, we mean a degree $d\in H_2(X)$ which is minimal with the property that $q^d$ occurs (with non-zero coefficient) in the quantum product $\sigma_u\star\sigma_v$ of two Schubert classes $\sigma_u$ and $\sigma_v$, where $\star$ denotes the product in the (small) quantum cohomology ring $\mathit{QH}^*(X)$ attached to $X$. Along the way, we prove that $\overline{M}_{0,3}(X,d)$ is quasi-homogeneous under the action of $G$ for all minimal degrees $d$ in $H_2(X)$ except for one instance of $G$, $P$ and $d$ which occurs in type $\mathsf{G}_2$.