Twisting the quantum grassmannian

Abstract

In contrast to the classical and semiclassical settings, the Coxeter element (12... n) which cycles the columns of an m x n matrix does not determine an automorphism of the quantum grassmannian. Here, we show that this cycling can be obtained by means of a cocycle twist. A consequence is that the torus invariant prime ideals of the quantum grassmannian are permuted by the action of the Coxeter element (12 ... n). We view this as a quantum analogue of the recent result of Knutson, Lam and Speyer, where the Lusztig strata of the classical grassmannian are permuted by (12... n).