### Abstract

Language | English |
---|---|

Article number | P5 |

Number of pages | 14 |

Journal | The Electronic Journal of Combinatorics |

Volume | 18 |

Issue number | 2 |

Publication status | Published - 13 Mar 2011 |

### Fingerprint

### Keywords

- permutation statistics
- mesh patterns
- André permutations
- simsun permutations
- Mahonian statistics

### Cite this

*The Electronic Journal of Combinatorics*,

*18*(2), [P5].

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*The Electronic Journal of Combinatorics*, vol. 18, no. 2, P5.

**Mesh patterns and the expansion of permutation statistics as sums of permutation patterns.** / Brändén, Petter; Claesson, Anders.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Mesh patterns and the expansion of permutation statistics as sums of permutation patterns

AU - Brändén, Petter

AU - Claesson, Anders

PY - 2011/3/13

Y1 - 2011/3/13

N2 - Any permutation statistic ƒ : S → C may be represented uniquely as a, possibly infinite, linear combination of (classical) permutation patterns: ƒ= ∑rλƒ (τ ) τ. To provide explicit expansions for certain statistics, we introduce a new type of permutation patterns that we call mesh patterns. Intuitively, an occurrence of the mesh pattern p = (π,R) is an occurrence of the permutation pattern with additional restrictions specified by R on the relative position of the entries of the occurrence. We show that, for any mesh pattern p = (π,R), we have λp(τ ) = (−1)|τ|−|π|p⋆( ) where p⋆ = (π,Rc) is the mesh pattern with the same underlying permutation as p but with complementary restrictions. We use this result to expand some well known permutation statistics, such as the number of left-to-right maxima, descents, excedances, fixed points, strong fixed points, and the major index. We also show that alternating permutations, André permutations of the first kind and simsun permutations occur naturally as permutations avoiding certain mesh patterns. Finally, we provide new natural Mahonian statistics.

AB - Any permutation statistic ƒ : S → C may be represented uniquely as a, possibly infinite, linear combination of (classical) permutation patterns: ƒ= ∑rλƒ (τ ) τ. To provide explicit expansions for certain statistics, we introduce a new type of permutation patterns that we call mesh patterns. Intuitively, an occurrence of the mesh pattern p = (π,R) is an occurrence of the permutation pattern with additional restrictions specified by R on the relative position of the entries of the occurrence. We show that, for any mesh pattern p = (π,R), we have λp(τ ) = (−1)|τ|−|π|p⋆( ) where p⋆ = (π,Rc) is the mesh pattern with the same underlying permutation as p but with complementary restrictions. We use this result to expand some well known permutation statistics, such as the number of left-to-right maxima, descents, excedances, fixed points, strong fixed points, and the major index. We also show that alternating permutations, André permutations of the first kind and simsun permutations occur naturally as permutations avoiding certain mesh patterns. Finally, we provide new natural Mahonian statistics.

KW - permutation statistics

KW - mesh patterns

KW - André permutations

KW - simsun permutations

KW - Mahonian statistics

UR - http://www.combinatorics.org/Volume_18/PDF/v18i2p5.pdf

UR - http://www.combinatorics.org/ojs/index.php/eljc/article/view/v18i2p5

M3 - Article

VL - 18

JO - The Electronic Journal of Combinatorics

T2 - The Electronic Journal of Combinatorics

JF - The Electronic Journal of Combinatorics

SN - 1077-8926

IS - 2

M1 - P5

ER -