Cyclic Sieving and Cluster Duality of Grassmannian

We introduce a decorated configuration space $\mathscr{C}\!\mathrm{onf}_n^\times(a)$ with a potential function $\mathcal{W}$. We prove the cluster duality conjecture of Fock–Goncharov for Grassmannians, that is, the tropicalization of $\big(\mathscr{C}\!\mathrm{onf}_n^\times(a), \mathcal{W}\big)$ canonically parametrizes a linear basis of the homogeneous coordinate ring of the Grassmannian $\operatorname{Gr}_a(n)$ with respect to the Plücker embedding. We prove that $\big(\mathscr{C}\!\mathrm{onf}_n^\times(a), \mathcal{W}\big)$ is equivalent to the mirror Landau–Ginzburg model of the Grassmannian considered by Eguchi–Hori–Xiong, Marsh–Rietsch and Rietsch–Williams. As an application, we show a cyclic sieving phenomenon involving plane partitions under a sequence of piecewise-linear toggles.