English

Symmetric and Asymptotically Symmetric Permutations

Combinatorics 2008-01-29 v1 Number Theory

Abstract

We consider two related problems arising from a question of R. Graham on quasirandom phenomena in permutation patterns. A ``pattern'' in a permutation σ\sigma is the order type of the restriction of σ:[n][n]\sigma : [n] \to [n] to a subset S[n]S \subset [n]. First, is it possible for the pattern counts in a permutation to be exactly equal to their expected values under a uniform distribution? Attempts to address this question lead naturally to an interesting number theoretic problem: when does k!k! divide (nk)\binom{n}{k}? Second, if the tensor product of a permutation with large random permutations is random-like in its pattern counts, what must the pattern counts of the original permutation be? A recursive formula is proved which uses a certain permutation ``contraction.''

Keywords

Cite

@article{arxiv.0801.4181,
  title  = {Symmetric and Asymptotically Symmetric Permutations},
  author = {Joshua Cooper and Andrew Petrarca},
  journal= {arXiv preprint arXiv:0801.4181},
  year   = {2008}
}

Comments

13 pages, 3 tables

R2 v1 2026-06-21T10:06:56.662Z