인문학
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자연과학
공학
의약학
농수해양학
예술체육학
복합학
지원사업
학술연구/단체지원/교육 등 연구자 활동을 지속하도록 DBpia가 지원하고 있어요.
커뮤니티
연구자들이 자신의 연구와 전문성을 널리 알리고, 새로운 협력의 기회를 만들 수 있는 네트워킹 공간이에요.
이용수
초록· 키워드
Let $D$ be an acyclic digraph. The competition graph of $D$ hasthe same set of vertices as $D$ and an edge between vertices $u$and $v$ if and only if there is a vertex $x$ in $D$ such that$(u,x)$ and $(v,x)$ are arcs of $D$. The competition number ofa graph $G$, denoted by $k(G)$, is the smallest number $k$ suchthat $G$ together with $k$ isolated vertices is the competitiongraph of an acyclic digraph. It is known to be difficult tocompute the competition number of a graph in general. Evencharacterizing the graphs with competition number one looks hard.In this paper, we continue the work done by Cho and Kim\cite{ck}to characterize the graphs with one hole and competition numberone. We give a sufficient condition for a graph with one hole tohave competition number one. This generates a huge class of graphswith one hole and competition number one. Then we completelycharacterize the graphs with one hole and competition number onethat do not have a vertex adjacent to all the vertices of thehole. Also we show that deleting pendant vertices from a connectedgraph does not change the competition number of the original graphas long as the resulting graph is not trivial, and this allows usto construct infinitely many graph having the same competitionnumber. Finally we pose an interesting open problem.
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