Block Numbers of Permutations and Schur-Positivity
Séminaire lotharingien de combinatoire, 78B (2017)
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The block number of a permutation is the maximal number of components in its expression as a direct sum. We show that the distribution of the set of left-to-right-maxima over 321-avoiding permutations with a given block number k is equal to the distribution of this set over 321-avoiding permutations with the last descent of the inverse permutation at position n-k. This result is analogous to the Foata-Schützenberger equi-distribution theorem, and implies Schur-positivity of the quasi-symmetric generating function of descent set over 321-avoiding permutations with a prescribed block number.
@article{SLC_2017_78B_a63,
author = {Ron M. Adin and Eli Bagno and Yuval Roichman},
title = {Block {Numbers} of {Permutations} and {Schur-Positivity}},
journal = {S\'eminaire lotharingien de combinatoire},
publisher = {mathdoc},
volume = {78B},
year = {2017},
url = {http://geodesic.mathdoc.fr/item/SLC_2017_78B_a63/}
}
Ron M. Adin; Eli Bagno; Yuval Roichman. Block Numbers of Permutations and Schur-Positivity. Séminaire lotharingien de combinatoire, 78B (2017). http://geodesic.mathdoc.fr/item/SLC_2017_78B_a63/