Extending kernel perfect digraphs to kernel perfect critical digraphs
نویسندگان
چکیده
منابع مشابه
On kernel-perfect critical digraphs
In this paper we investigate new sufficient conditions for a digraph to be kernel-perfect (KP) and some structural properties of kernel-perfect critical (KPC) digraphs. In particular, it is proved that the asymmetrical part of any KPC digraph is strongly connected. A new method to construct KPC digraphs is developed. The existence of KP and KPC digraphs with arbitrarily large dichromatic number...
متن کاملKernel perfect and critical kernel imperfect digraphs structure
A kernel N of a digraph D is an independent set of vertices of D such that for every w ∈ V (D)−N there exists an arc from w to N . If every induced subdigraph of D has a kernel, D is said to be a kernel perfect digraph. Minimal non-kernel perfect digraph are called critical kernel imperfect digraph. If F is a set of arcs of D, a semikernel modulo F , S of D is an independent set of vertices of ...
متن کاملSome results on the structure of kernel-perfect and critical kernel-imperfect digraphs
A kernel N of a digraph D is an independent set of vertices of D such that for every w ∈ V (D) − N there exists an arc from w to N . The digraph D is said to be a kernel-perfect digraph when every induced subdigraph of D has a kernel. Minimal non kernel-perfect digraphs are called critical kernel imperfect digraphs. In this paper some new structural results concerning finite critical kernel imp...
متن کاملExtending Digraphs to Digraphs with (without) k-Kernel
For any digraph D we construct a digraph s(S) such that D has a k-kernel iff s(S) has a k-kernel. The method employed allows to prove that, any digraph is an induced subdigraph of an infinite set of digraphs with (resp. without) k-kernel; and it can be used as a powerful tool in the construction of a large class of digraphs with (resp. without) k-kernel. Previous results are generalyzed. Mathem...
متن کاملNew classes of critical kernel-imperfect digraphs
A kernel of a digraph D is a subset N ⊆ V (D) which is both independent and absorbing. When every induced subdigraph of D has a kernel, the digraph D is said to be kernel-perfect. We say that D is a critical kernel-imperfect digraph if D does not have a kernel but every proper induced subdigraph of D does have at least one. Although many classes of critical kernel-imperfect-digraphs have been c...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1991
ISSN: 0012-365X
DOI: 10.1016/0012-365x(91)90023-u