On the Hilton-Spencer intersection theorems for unions of cycles
Abstract
A family of sets is said to be intersecting if every two sets in intersect. An intersecting family is said to be \emph{trivial} it its sets have a common element. A graph is said to be -EKR if at least one of the largest intersecting families of independent -element sets of is trivial. Let and denote the independence number and the clique number of , respectively. Hilton and Spencer recently showed that if is the vertex-disjoint union of a cycle raised to the power and cycles raised to the powers , respectively, , and then is -EKR. They had shown that the same holds if is replaced by a path and the condition on the clique numbers is relaxed to We use the classical Shadow Intersection Theorem of Katona to obtain a short proof of each result for the case where the inequality for the minimum clique number is strict.
Keywords
Cite
@article{arxiv.1908.08825,
title = {On the Hilton-Spencer intersection theorems for unions of cycles},
author = {Peter Borg and Carl Feghali},
journal= {arXiv preprint arXiv:1908.08825},
year = {2019}
}
Comments
9 pages