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Hamiltonicity and Degrees of Adjacent Vertices in Claw‐Free Graphs
Authors:Zhi‐Hong Chen
Institution:DEPARTMENT OF COMPUTER SCIENCE AND SOFTWARE ENGINEERING, BUTLER UNIVERSITY, INDIANAPOLIS, IN
Abstract:For a graph H , let urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0001 for every edge urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0002. For urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0003 and urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0004, let urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0005 be a set of k‐edge‐connected K3‐free graphs of order at most r and without spanning closed trails. We show that for given urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0006 and ε, if H is a k‐connected claw‐free graph of order n with urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0007 and urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0008, and if n is sufficiently large, then either H is Hamiltonian or the Ryjác?ek's closure urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0009 where G is an essentially k‐edge‐connected K3‐free graph that can be contracted to a graph in urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0010. As applications, we prove:
  • (i) For urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0011, if urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0012 and if urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0013 and n is sufficiently large, then H is Hamiltonian.
  • (ii) For urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0014, if urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0015 and n is sufficiently large, then H is Hamiltonian.
These bounds are sharp. Furthermore, since the graphs in urn:x-wiley:03649024:media:jgt22120:jgt22120-math-0016 are fixed for given p and can be determined in a constant time, any improvement to (i) or (ii) by increasing the value of p and so enlarging the number of exceptions can be obtained computationally.
Keywords:degree of adjacent vertices  dominating closed trail  Hamiltonian cycle
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