Vacillating Hecke Tableaux and Linked Partitions
We introduce the structure of vacillating Hecke tableaux, and establish a one-to-one correspondence between vacillating Hecke tableaux and linked partitions by using the Hecke insertion algorithm developed by Buch, Kresch, Shimozono, Tamvakis and Yong. Linked partitions arise in free probability theory. Motivated by the Hecke insertion algorithm, we define a Hecke diagram as a Young diagram possibly with a marked corner. A vacillating Hecke tableau is defined as a sequence of Hecke diagrams subject to certain addition and deletion of rook strips. The notion of a rook strip was introduced by Buch in the study of the Littlewood-Richardson rule for stable Grothendieck polynomials. A rook strip is a skew Young diagram with at most one square in each row and column. We show that the crossing number and the nesting number of a linked partition can be determined by the maximal number of rows and the maximal number of columns of the diagrams in the corresponding vacillating Hecke tableau. The proof relies on a theorem due to Thomas and Yong concerning the lengths of the longest strictly increasing and the longest strictly decreasing subsequences in a word. This implies that the crossing number and the nesting number have a symmetric joint distribution over linked partitions, confirming a conjecture of de Mier. We also prove a conjecture of Kim which states that the crossing number and the nesting number have a symmetric joint distribution over the front representations of partitions.