On canonical antichains

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• 作者：Guoli Ding
• 关键词：Well-quasi-ordering ; Infinite antichain ; Subgraph ; Induced subgraph
• 刊名：Discrete Mathematics
• 出版年：2009
• 出版时间：28 March 2009
• 年：2009
• 卷：309
• 期：5
• 页码：1123-1134
• 全文大小：698 K

文摘

An antichain A of a well-founded quasi-order Q is canonical if for every ideal F of Q, F has an infinite antichain if and only if F∩A is infinite. In this paper we characterize the obstructions to having a canonical antichain. As an application we show that, under the induced subgraph relation, the class of finite graphs does not have a canonical antichain. In contrast, this class does have a canonical antichain with respect to the subgraph relation.