这是群论和图论方向的线上系列报告，我们希望能够促进国内外青年学者（博士生为主）在群论和图论研究上的交流。报告主题分布在（但不限于）以下研究方向：
This is a platform for young group theorists and graph theorists (mostly PhD students) to talk about their research and related topics online. The topic can be anything related to group theory and graph theory, including but not limited to the following.
一般地，系列报告定期于北京时间每周三下午16:00-17:00进行。
Our usual time is Wednesday 16:00-17:00 (GMT+8).
Title: Vertex-transitive graphs and derangements
Speaker: Marco Barbieri (University of Pavia & University of Milano-Bicocca)
Time: 16:00-17:00 (GMT+8), Wednesday October 9th
Location: Zoom: 616 601 4311 (passcode: gts2024)
Abstract:
A derangement is a permutation without any fixed points.
An outstanding property of derangements in a finite transitive permutation group is their abundance.
What can we say about the portion of derangements of a group acting transitively on the vertices of a graph?
In the present talk, we will introduce a lower bound on the portion of derangements depending only on the valency of the graph, and we will discuss its asymptotic behaviour compared to other general lower bounds.
The seminar is currently based at the Southern University of Science and Technology (SUSTech, 南方科技大学).