题目：Steiner triple systems with few parallel classes

报告人: Daniel Horsley博士, Monash University

Abstract:  A Steiner triple system of order v (or STS(v)) is a pair (V, B) where V is a v-set and B is a set of 3-subsets of V (called triples) such that each pair of elements of V occurs in exactly one triple in B. Such a system exists if and only if v=6k+1 or v=6k+3 for some integer k. A parallel class of an STS(6k+3) is a set of its triples that forms a partition of its point set.

In 2015, Darryn Bryant and I constructed the first known infinite family of STS(6k+3)s without parallel classes. More recently, together with Charles Colbourn and Ian Wanless, we were able to use similar methods to find, for all k, STS(6k+3)s with ``few'' (sublinearly many in k) disjoint parallel classes. This talk will discuss these results and their context.

时间：10月20日（周六）上午10:30--11:30

地点：首都师大新教2楼 727 教室

欢迎全体师生积极参加！