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Cycle‐Saturated Graphs with Minimum Number of Edges
Authors:Zoltán Füredi  Younjin Kim
Institution:1. DEPARTMENT OF MATHEMATICS, UNIVERSITY OF ILLINOIS, , URBANA, ILLINOIS;2. RéNYI INSTITUTE OF MATHEMATICS OF THE HUNGARIAN, ACADEMY OF SCIENCES, , BUDAPEST, P.O. BOX 127 HUNGARY;3. DEPARTMENT OF MATHEMATICS, UNIVERSITY OF ILLINOIS AT URBANA‐CHAMPAIGN, , URBANA, ILLINOIS
Abstract:A graph G is called H‐saturated if it does not contain any copy of H, but for any edge e in the complement of G, the graph urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0001 contains some H. The minimum size of an n‐vertex H‐saturated graph is denoted by urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0002. We prove urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0003 holds for all urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0004, where urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0005 is a cycle with length k. A graph G is H‐semisaturated if urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0006 contains more copies of H than G does for urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0007. Let urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0008 be the minimum size of an n‐vertex H‐semisaturated graph. We have urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0009 We conjecture that our constructions are optimal for urn:x-wiley:03649024:media:jgt21668:jgt21668-math-0010. © 2012 Wiley Periodicals, Inc. J. Graph Theory 73: 203–215, 2013
Keywords:graphs  cycles  extremal graphs  minimal saturated graphs
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