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## 第93回 2019年5月17日 14:00〜15:30

Xingzhi Zhan（East China Normal University）「The maximum girth and minimum circumference of graphs with prescribed radius and diameter」

Ostrand posed the following two questions in 1973. (1) What is the maximum girth of a graph with radius $r$ and diameter $d$? (2) What is the minimum circumference of a graph with radius $r$ and diameter $d$? We describe the answers to these two questions and explain the basic ideas. In the second part of this talk we report on the recent solution of two conjectures on the status sequence of graphs. This is joint work with Pu Qiao.