It is well known that a graph G of orderp 2 3 is Hamilton-connected if d(u) +d(v) 2 p + 1 for each pair of nonadjacent vertices u and w. In this paper we consider connected graphs G of order at least 3 for which where N ( z ) denote the neighborhood of a vertex z. We prove that a graph G satisfying
On graphs satisfying a local ore-type condition
✍ Scribed by Asratian, A. S.; Broersma, H. J.; Van den Heuvel, J.; Veldman, H. J.
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 497 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0364-9024
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✦ Synopsis
For an integer i, a graph is called an L,-graph if, for each triple of vertices u, u , w with
and Khachatrian proved that connected Lo-graphs of order a t least 3 are hamiltonian, thus improving Ore's Theorem. All K1,3-free graphs are L1-graphs, whence recognizing hamiltonian L1-graphs is an NP-complete problem. The following results about L1graphs, unifying known results of Ore-type andknown results on Kl,3-free graphs, are obtained. Set X = {GIKp,p+l C G C Kp v Kp+l for some p 2 2) ( V denotes join).
If G is a 2-connected L1-graph, then G is I-tough unless G E 5%. Furthermore, if G is a connected L1-graph of order at least 3 such that IN(u) f-N(u)l L 2 for every pair of vertices u, u with d(u, U ) = 2, then G is hamiltonian unless G E X , and every pair of vertices x, y with d(x, y) L 3 is connected by a Hamilton path. This result implies that of Asratian and Khachatrian. Finally, if G is a connected L1-graph of even order, then G has a perfect matching.
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