Abstract We characterise digraphs of directed treewidth one in terms of forbidden butterfly minors and in terms of the structure of the cycle hypergraph to a digraph D , i.e. the hypergraph on vertex set V ( D ) whose hyperedges correspond to the vertex sets of directed cycles in D .

中文翻译：

---

有向树宽一的有向图

摘要 我们根据禁止蝴蝶次要线和有向图 D 的循环超图的结构来刻画有向树宽一的有向图，即顶点集 V ( D ) 上的超图，其超边对应于有向循环的顶点集D.