Tuesday, January 28, 2020

Yash Lodha, EPFL, Lausanne

Title: The von Neumann-Day problem for finitely presented groups.

Speaker: Yash Lodha, EPFL, Lausanne
Where: Seminar Room, School of Physical Sciences (SPS), C V Raman Marg, JNU
When: Tuesday, January 28, 2020, 4 PM


The so called von Neumann-Day problem asks if there exist nonamenable groups that do not contain nonabelian free subgroups. I will describe a recent solution to the problem for the class of torsion free finitely presented groups (joint with Justin Moore). The groups emerge as groups of homeomorphisms of the real line, and an encoding by means of continued fractions is used to prescribe a certain combinatorial structure. This structure allows us to establish that the groups are finitely presented.