报告题目：A Characterization of Iterated Line Graphs
报 告 人：冯荣权教授（北京大学）
报告摘要：Let X be a graph with edge set E(X). The line graph L(X) of X is the graph with vertex set E(X) and two vertices are adjacent in L(X) if and only if the corresponding edges share precisely one common vertex in X. The n-th iterated line graph Ln(X) of X is defined recursively by L1(X) = L(X) and Ln(X) = L(Ln?1(X)) for n > 1. In this talk, normal walks of norm s, which is a generalization of s-arcs in a graph, are defined and their additive properties are studied. As a result, a characterization of iterated line graphs is given in terms of normal walk graphs constructed by normal walks.