Cohomology in singular blocks of parabolic category $\mathcal{O}$ (2210.02269v2)

Abstract: We determine the dimensions of $\mathrm{Ext}$-groups between simple modules and dual generalized Verma modules in singular blocks of parabolic versions of category $\mathcal{O}$ for complex semisimple Lie algebras and affine Kac-Moody algebras.