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A Combined Logarithmic Bound on the Chromatic Index of Multigraphs
Authors:Michael Plantholt
Institution:DEPARTMENT OF MATHEMATICS, ILLINOIS STATE UNIVERSITY, , NORMAL, ILLINOIS, 61790‐4520
Abstract:For a multigraph G, the integer round‐up urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0001 of the fractional chromatic index urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0002 provides a good general lower bound for the chromatic index urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0003. For an upper bound, Kahn 1996 showed that for any real urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0004 there exists a positive integer N so that urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0005 whenever urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0006. We show that for any multigraph G with order n and at least one edge, urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0007). This gives the following natural generalization of Kahn's result: for any positive reals urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0008, there exists a positive integer N so that urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0009 + c urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0010 whenever urn:x-wiley:03649024:media:jgt21670:jgt21670-math-0011. We also compare the upper bound found here to other leading upper bounds.
Keywords:chromatic index  fractional chromatic index  multigraph
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