# Refined inversion statistics on permutations

### Electronic Journal of Combinatorics, Volume 19 (2012)

We introduce and study new refinements of inversion statistics for permutations, such as k-step inversions, (the number of inversions with fixed position differences) and non-inversion sums (the sum of the differences of positions of the non-inversions of a permutation). We also provide a distribution function for non-inversion sums, a distribution function for k-step inversions that relates to the Eulerian polynomials, and special cases of distribution functions for other statistics we introduce, such as (\leq k)-step inversions and (k_1,k_2)-step inversions (that fix the value separation as well as the position). We connect our refinements to other work, such as inversion tops that are 0 modulo a fixed integer d, left boundary sums of paths, and marked meshed patterns. Finally, we use non-inversion sums to show that for every number n>34, there is a permutation such that the dot product of that permutation and the identity permutation (of the same length) is n.

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## Presentations

- Counting special inversions in permutations, Mathematics Colloquium, University of Iceland, Reykjavik, Iceland, November 2010 (Joshua presented)
- Counting special inversions in permutations, Mathematics Colloquium, California State University, Long Beach, California, December 2010 (Henning presented)
- Refined inversion statistics on permutations, 2012 Joint Mathematics Meetings, Boston, MA, January 2012 (Joshua presented)