Crystals and trees: quasiKashiwara operators, monoids of binary trees, and RobinsonSchenstedtype correspondences
Abstract
Kashiwara's crystal graphs have a natural monoid structure that arises by identifying words labelling vertices that appear in the same position of isomorphic components. The celebrated plactic monoid (the monoid of Young tableaux), arises in this way from the crystal graph for the $q$analogue of the general linear Lie algebra $\mathfrak{gl}_{n}$, and the socalled Kashiwara operators interact beautifully with the combinatorics of Young tableaux and with the RobinsonSchenstedKnuth correspondence. The authors previously constructed an analogous `quasicrystal' structure for the related hypoplactic monoid (the monoid of quasiribbon tableaux), which has similarly neat combinatorial properties. This paper constructs an analogous `crystaltype' structure for the sylvester and Baxter monoids (the monoids of binary search trees and pairs of twin binary search trees, respectively). Both monoids are shown to arise from this structure just as the plactic monoid does from the usual crystal graph. The interaction of the structure with the sylvester and Baxter versions of the RobinsonSchenstedKnuth correspondence is studied. The structure is then applied to prove results on the number of factorizations of elements of these monoids, and to prove that both monoids satisfy nontrivial identities.
 Publication:

arXiv eprints
 Pub Date:
 February 2017
 arXiv:
 arXiv:1702.02998
 Bibcode:
 2017arXiv170202998C
 Keywords:

 Mathematics  Combinatorics;
 Mathematics  Group Theory;
 05E15 (Primary);
 05C05;
 05E05;
 20M05 (Secondary)
 EPrint:
 32 pages