منابع مشابه
Kernels and perfectness in arc-local tournament digraphs
In this paper we give a characterization of kernel-perfect (and of critical kernel-imperfect) arc-local tournament digraphs. As a consequence, we prove that arc-local tournament digraphs satisfy a strenghtened form of the following interesting conjecture which constitutes a bridge between kernels and perfectness in digraphs, stated by C. Berge and P. Duchet in 1982: a graph G is perfect if and ...
متن کاملMaximal m-free digraphs ——– A generalization of tournament graphs
We call a digraph D = (V,E) a maximal m-free digraph if only if D has no cycles of length at most m and adding any ordered pair (u, v) 6∈ E will create a cycle of length at most m. In this note, we investigate this special class of digraphs. We will show that these digraphs share similar properties with tournament digraphs and this ”maximality” condition can be used to solve several extremal pr...
متن کامل0n removable cycles in graphs and digraphs
In this paper we define the removable cycle that, if $Im$ is a class of graphs, $Gin Im$, the cycle $C$ in $G$ is called removable if $G-E(C)in Im$. The removable cycles in Eulerian graphs have been studied. We characterize Eulerian graphs which contain two edge-disjoint removable cycles, and the necessary and sufficient conditions for Eulerian graph to have removable cycles h...
متن کاملMore skew-equienergetic digraphs
Two digraphs of same order are said to be skew-equienergetic if their skew energies are equal. One of the open problems proposed by Li and Lian was to construct non-cospectral skew-equienergetic digraphs on n vertices. Recently this problem was solved by Ramane et al. In this paper, we give some new methods to construct new skew-equienergetic digraphs.
متن کاملImbalance in tournament designs
We introduce two measures of imbalance, the team imbalance, and the field imbalance, in a tournament design. In addition to an exhaustive study of imbalances in tournament designs with up to eight teams, we present some bounds on the imbalances, as well as recursive constructions for homogeneous tournaments.
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ژورنال
عنوان ژورنال: Journal of Combinatorial Theory, Series B
سال: 1993
ISSN: 0095-8956
DOI: 10.1006/jctb.1993.1069