From December 2020 till March 2021, Jack Davies and I organised a reading group on synthetic spectra. There are some notes on the seminar website.
Together with the topologists in Nijmegen, we (topologists in Utrecht) have a joint seminar, called Topology InterCity Seminar Utrecht-Nijmegen.
In Spring 2020, Gijs Heuts, Mingcong Zeng and I organised the master student seminar about exotic spheres.
From Fall 2019 to Spring 2020, Jack Davies, Magdalena Kedziorek, Tommy Lundemo, Mingcong Zeng, and I had a a reading seminar on chromatic homotopy theory. In the seminar, we studied nilpotency and periodicity theorem by Devinatz, Hopkins and Smith, some fundamental work of Ravenel, as well as basic notion of tensor triangulated geometry and its application on the classification of thick tensor ideals of the G-equivariant stable homotopy category. There are some notes on the seminar website.