Forbidding just one intersection, for permutations
Abstract
We prove that for sufficiently large, if is a family of permutations of with no two permutations in agreeing exactly once, then , with equality holding only if is a coset of the stabilizer of 2 points. We also obtain a Hilton-Milner type result, namely that if is such a family which is not contained within a coset of the stabilizer of 2 points, then it is no larger than the family . We conjecture that for , and for sufficiently large depending on , if is family of permutations of with no two permutations in agreeing exactly times, then , with equality holding only if is a coset of the stabilizer of points. This can be seen as a permutation analogue of a conjecture of Erd\H{o}s on families of -element sets with a forbidden intersection, proved by Frankl and F\"uredi in [P. Frankl and Z. F\"uredi, Forbidding Just One Intersection, Journal of Combinatorial Theory, Series A, Volume 39 (1985), pp. 160-176].
Cite
@article{arxiv.1310.8108,
title = {Forbidding just one intersection, for permutations},
author = {David Ellis},
journal= {arXiv preprint arXiv:1310.8108},
year = {2013}
}
Comments
26 pages