The closure of the set of periodic modules over a concealed canonical algebra is regular in codimension one

Let Λ be a concealed canonical algebra and d the dimension vector of a Λ-module which is periodic respect to the action of the Auslander-Reiten translation τ. In the paper, we investigate the union of the closures of the orbits of the τ-periodic Λ-modules of dimension vector d. We show that this set is closed and regular in codimension one.