We present and prove several results concerning the length of longest cycles in 2connected or I-tough graphs with large degree sums. These results improve many known results on long cycles in these graphs. We also consider the sharpness of the results and discuss some possible strengthenings.
Long dominating cycles and paths in graphs with large neighborhood unions
โ Scribed by H. J. Broersma; H. J. Veldman
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 413 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0364-9024
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โฆ Synopsis
Abstract
Let G be a graph of order n and define NC(G) = min{|N(u) โช N(v)| |uv โ E(G)}. A cycle C of G is called a dominating cycle or Dโcycle if V(G) โ V(C) is an independent set. A Dโpath is defined analogously. The following result is proved: if G is 2โconnected and contains a Dโcycle, then G contains a Dโcycle of length at least min{n, 2__NC__(G)} unless G is the Petersen graph. By combining this result with a known sufficient condition for the existence of a Dโcycle, a common generalization of Ore's Theorem and several recent โneighborhood union resultsโ is obtained. An analogous result on long Dโpaths is also established.
๐ SIMILAR VOLUMES
## Abstract Let __G__ be a simple graph of order __n__ and minimal degree >โcn (0โ<โcโ<โ1/2). We prove that (1) There exist __n__~0~โ=โ__n__~0~(__c__) and __k__โ=โ__k__(__c__) such that if __n__โ>โ__n__~0~ and __G__ contains a cycle __C__~__t__~ for some __t__โ>โ2__k__, then __G__ contains a cycle
## Abstract Sufficient degree conditions for the existence of properly edgeโcolored cycles and paths in edgeโcolored graphs, multigraphs and random graphs are investigated. In particular, we prove that an edgeโcolored multigraph of order __n__ on at least three colors and with minimum colored degre
## Abstract It is proved that for every positive integers __k__, __r__ and __s__ there exists an integer __n__โ=โ__n__(__k__,__r__,__s__) such that every __k__โconnected graph of order at least __n__ contains either an induced path of length __s__ or a subdivision of the complete bipartite graph __
## Abstract A set __S__ of vertices in a graph __G__ is a total dominating set of __G__ if every vertex of __G__ is adjacent to some vertex in __S__. The minimum cardinality of a total dominating set of __G__ is the total domination number ฮณ~t~(__G__) of __G__. It is known [J Graph Theory 35 (2000)