EQUIVARIANT RIGIDITY OF RICHARDSON VARIETIES

We prove that Schubert and Richardson varieties in flag manifolds are uniquely determined by their equivariant cohomology classes, as well as a stronger result that replaces Schubert varieties with closures of Białynicki-Birula cells under suitable conditions. This is used to prove a conjecture of Buch, Chaput, and Perrin, stating that any two-pointed curve neighborhood representing a quantum cohomology product with a Seidel class is a Schubert variety. We pose a stronger conjecture which implies a Seidel multiplication formula in equivariant quantum K-theory, and prove this conjecture for cominuscule flag varieties.