ISSN 1234-3099 (print version)

ISSN 2083-5892 (electronic version)

Discussiones Mathematicae Graph Theory

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Discussiones Mathematicae Graph Theory


Discussiones Mathematicae Graph Theory 32(2) (2012) 379-382
DOI: 10.7151/dmgt.1620

Erdös--Ko--Rado from Intersecting Shadows

Gyula O.H. Katona and Ákos Kisvölcsey

Alfréd Rényi Institute of Mathematics,
Hungarian Academy of Sciences
1053 Budapest, Reáltanoda u. 13--15, Hungary


A set system is called t-intersecting if every two members meet each other in at least t elements. Katona determined the minimum ratio of the shadow and the size of such families and showed that the Erdős-Ko-Rado theorem immediately follows from this result. The aim of this note is to reproduce the proof to obtain a slight improvement in the Kneser graph. We also give a brief overview of corresponding results.

Keywords: Kneser graph, coclique, intersecting family, shadow

2010 Mathematics Subject Classification: 05C35, 05D05.


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Received 28 April 2011
Revised 6 August 2011
Accepted 8 August 2011