Asymptotics of the total chromatic number for multigraphs

نویسنده

  • Peter Mark Kayll
چکیده

For loopless multigraphs, the total chromatic number is asymptotically its fractional counterpart as the latter invariant tends to infinity. The proof of this is based on a recent theorem of Kahn establishing the analogous asymptotic behaviour of the list-chromatic index for multigraphs. The total colouring conjecture, proposed independently by Behzad [1] and Vizing [11], asserts that the total chromatic number X t of a simple graph exceeds the maximum degree ~ by at most two. The most recent increment (better: giant leap) toward a proof of this conjecture was made by Molloy and Reed [8], who established by probabilistic means that the difference between X t and ~ is at most a constant ( say c). An immediate consequence of their result is that for simple graphs, X t is asymptotically its fractional analogue X: as the latter tends to infinity: for this follows from ~ + 1 :::; X: :::; X t :::; ~ + c. This leads naturally to the following question: does X t enjoy the same asymptotic connection with X: for loopless multigraphs (henceforth multigraphs)? That this question has an affirmative answer was conjectured in [6]. The purpose of this note is to verify that conjecture: Theorem 1 For multigraphs,

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عنوان ژورنال:
  • Australasian J. Combinatorics

دوره 19  شماره 

صفحات  -

تاریخ انتشار 1999