西安电子科技大学张欣副教授 ；福州大学侯建锋教授 学术报告

Bollob\'as and Scott [Problems and results on judicious partitions, Random Struct. Alg. 21 (2002) 414--430] asked for conditions that guarantee a bisection of a graph  with $m$ edges in which each class has at most $(1/4+o(1)\big)m$ edges. We demonstrate that cycles of length 4 play an important role for this question, and give some results on this topic.