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The Largest Minimum Codegree of a 3-Graph Without a Generalized 4-Cycle

Published online by Cambridge University Press:  19 October 2012

EDWARD MARCHANT
EDWARD MARCHANT*
Affiliation:
Department of Pure Mathematics and Mathematical Statistics, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WB, UK (e-mail: ejmarchant@gmail.com)
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Abstract

A 3-graph is said to contain a generalized 4-cycle if it contains 4 edges A, B, C, D such that A ∩ B=C ∩ D =∅ and A ∪ B=C ∪ D. We show that a 3-graph in which every pair of vertices is contained in at least 4 edges must contain a generalized 4-cycle. When the number of vertices, n, is equivalent to 1 or 5 modulo 20, this result is optimum, in the sense that for such n there are 3-graphs where every pair of vertices is contained in 3 edges but which do not contain a generalized 4-cycle.

Keywords

Primary 05C65Secondary 05C35
Type
Paper
Information
Combinatorics, Probability and Computing , Volume 22 , Issue 1 , January 2013 , pp. 112 - 117
Copyright
Copyright © Cambridge University Press 2012

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