We generalize a result by Maghout who had shown that every tournament of radius 2 admits three distinct centers. Here we prove that every graph without kernel has at least three distinct quasi-kernels.
Kernels in a special class of digraphs
✍ Scribed by H. Galeana-Sánchez; Xueliang Li
- Book ID
- 108316221
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 421 KB
- Volume
- 178
- Category
- Article
- ISSN
- 0012-365X
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📜 SIMILAR VOLUMES
## Abstract A vertex set __X__ of a digraph __D__ = (__V, A__) is a __kernel__ if __X__ is independent (i.e., all pairs of distinct vertices of __X__ are non‐adjacent) and for every __v__ ∈ __V__‐__X__ there exists __x__ ∈ __X__ such that __vx__ ∈ __A__. A vertex set __X__ of a digraph __D__ = (__V
For the class of 2-diregular digraphs: (1) We give a simple closed form expression-a power of 2-for the number of difactors. (2) For the adjacency matrices of these graphs, we show an intimate relationship between the permanent and determinant. (3) We give a necessary and sufficient condition for th
In this paper we present some results on the existence of /c-kernels and (k, [)-kernels in digraphs which generalize the following Theorem of P. Duchet [2]: "If every directed cycle of odd length in a digraph D has at least two symmetrical arcs, then D has a kernel.