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Perfect Matchings Avoiding Several Independent Edges in a Star‐Free Graph
Authors:Yoshimi Egawa  Michitaka Furuya
Institution:DEPARTMENT OF MATHEMATICAL INFORMATION SCIENCE, TOKYO UNIVERSITY OF SCIENCE, SHINJUKU‐KU, JAPAN
Abstract:In Aldred and Plummer (Discrete Math 197/198 (1999) 29–40) proved that every m‐connected urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0001‐free graph of even order has a perfect matching M with urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0002 and urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0003, where F1 and F2 are prescribed disjoint sets of independent edges with urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0004 and urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0005. It is known that if l satisfies urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0006, then the star‐free condition in the above result is best possible. In this paper, for urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0007, we prove a refinement of the result in which the condition is replaced by the weaker condition that G is urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0008‐free (note that the new condition does not depend on l). We also show that if m is even and either urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0009 or urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0010, then for m‐connected graphs G with sufficiently large order, one can replace the condition by the still weaker condition that G is urn:x-wiley:03649024:media:jgt21883:jgt21883-math-0011‐free. The star‐free conditions in our results are best possible.
Keywords:perfect matching  forbidden subgraphs  extendability
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