Abstract: Extreme amenability is a remarkable property for a topological group to have. Ever since the first example of such groups was constructed in 1975, many groups have been shown to be extremely amenable. In this talk, I will address the question: How many pairwise non-isomorphic extremely amenable groups are there? We demonstrate that there are continuum many pairwise non-isomorphic extremely amenable groups which are automorphism groups of countable structures, and in particular Polish. I will also talk about some related results from the point of view of descriptive set theory. This is joint work with Mahmood Etedadialiabadi and Feng Li.

个人简介：高速（Gao Su），本科毕业于北京大学数学系，博士毕业于UCLA，现任南开大学讲席教授，曾任美国北得克萨斯大学校董讲席教授、数学系主任、理学院院长。主要研究领域是数理逻辑、数学基础及其在基础数学其它分支中的应用。他用描述集合论的方法研究数学中多个领域中分类问题的复杂度，解决了多个重要公开问题，取得的成果涵盖代数、几何、拓扑、泛函分析、动力系统等多个数学分支，发表在Inventiones Mathematicae等国际一流数学期刊。