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A note on induced cycles in Kneser graphs
Authors:Y Kohayakawa
Institution:1. Department of Pure Mathematics and Mathematical Statistics, University of Cambridge, 16 Mill Lane, CB2 1SB, Cambridge, England
Abstract:Letg(n,r) be the maximal order of an induced cycle in the Knesser graph Kn(n] r), whose vertices are ther-sets of n]={1, ...,n} and whose adjacency relation is disjointness. Thusg(n, r) is the largestm for which there is a sequenceA 1,A 2,...,A m ugr n] ofr-sets withA i capA j=thetav if and only if |i-j|=1 orm–1. We prove that there is an absolute constantc>0 for which

$$g(2r + 1,r) > c(2.587)^r $$
Keywords:AMS subject classification (1980)" target="_blank">AMS subject classification (1980)  05 C 35  05 C 65
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