Some permutations on Dyck words

We examine three permutations on Dyck words. The first one, alpha, is related to the Baker and Norine theorem on graphs, the second one, beta, is the symmetry, and the third one is the composition of these two. The first two permutations are involutions and it is not difficult to compute the number of their fixed points, while the third one has cycles of different lengths. We show that the lengths of these cycles are odd numbers. This result allows us to give some information about the interplay between alpha and beta, and a characterization of the fixed points of alpha circle beta. 2016 Elsevier B.V. All rights reserved.