A bump statistic on permutations resulting from the Robinson-Schensted correspondence

Abstract

In this paper we investigate a permutation statistic that was independently introduced by Romik in 2005. This statistic counts the number of bumps that occur during the execution of the Robinson-Schensted procedure when applied to a given permutation. We provide several interpretations of this bump statistic that include the tableaux shape and also as an extremal problem concerning permutations and increasing subsequences. Several aspects of this bump statistic are investigated from both structural and enumerative viewpoints.