Seminar Algebra and Topology

The seminar usually takes place Wednesdays in F.13.11, 16:30 - 17:30.
Involved professors: Jens Hornbostel, Sascha Orlik, Kay Rülling, Tobias Schmidt, Britta Späth, Matthias Wendt.

 

Zhu: Multiplication on the Real Brown–Peterson Spectrum

The development of brave new algebra was much guided by the problem of finding the full multiplicative structure of the Brown–Peterson spectrum and its truncated variants. While this has seen a thorough study throughout history, the C2-equivariant analogue for the Real Brown–Peterson spectrum has essentially been left completely open. In joint work with Ryan Quinn, we remedy this situation by developing an obstruction theory to lifting structured orientations. Powered by the engine of Wilson space theory, we manage to give the first structured versions of the Real Brown–Peterson spectrum and its truncated cousins.

Martin: The Enriques surface of minimal entropy

Salem numbers appear naturally as dynamical degrees of isometries of hyperbolic lattices and hence in the study of entropy of surface automorphisms. The conjecturally smallest Salem number is Lehmer's number $\lambda_{10}$, which can be realized by automorphisms of K3 surfaces and rational surfaces by work of McMullen. In this talk, I will explain how to generalize a result of Oguiso asserting the non-realizability of $\lambda_{10}$ for automorphisms of Enriques surfaces over the complex numbers to odd characteristics. Then, I will describe the unique counterexample in characteristic 2. This is joint work with Giacomo Mezzedimi and Davide Veniani.

• Gästeseminare vergangener Semester