Group actions with spectral gap on surfaces

  • Venue:

    20.30 SR 2.058

  • Date:

    19.01.2023

  • Speaker:

    Tim de Laat

  • Time:

    15:45

  • Spectral gap is an important rigidity property for group actions with various applications. One of these applications is the construction of families of expander graphs. I will explain a new class of actions with spectral gap on surfaces of arbitrary genus. These are the first examples of actions with spectral gap on surfaces of genus g > 1. I will also explain some of the surprising large-scale geometric features of the expander families constructed from these actions. This is joint work with Goulnara Arzhantseva, Dawid Kielak, and Damian Sawicki.