Twisting the quantum grassmannian

In contrast to the classical and semiclassical settings, the Coxeter element (12...n) which cycles the columns of an mxn matrix does not determine an automorphism of the quantum grassmannian. Here, we show that this cycling can be obtained by defining 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 that the Lusztig strata of the classical grassmannian are permuted by (12...n).