Guest lectures and seminars - Page 122

We will discuss the motivic May spectral sequence and demonstrate how to  use it to identify Massey products in the motivic Adams spectral sequence.  We will then investigate what is known about the motivic homotopy groups  of the eta-local sphere over the complex numbers and discuss how these  calculations may work over other base fields.  

Francesco Galuppi (UiO/Ferrara) gives the algebraic geometry seminar:

"Identifiability of polynomials and Cremona transformations."

Certain 3-dimensional lens spaces are known to smoothly bound 4-manifolds with the rational homology of a ball. These can sometimes be useful in cut-and-paste constructions of interesting (exotic) smooth 4-manifolds. To this end it is interesting to identify 4-manifolds which contain these rational balls. Khodorovskiy used Kirby calculus to exhibit embeddings of rational balls in certain linear plumbed 4-manifolds, and recently Park-Park-Shin used methods from the minimal model program in 3-dimensional complex algebraic geometry to generalise Khodorovskiy's result. The goal of this talk is to give an accessible introduction to the objects mentioned above and also to describe a much easier topological proof of Park-Park-Shin's theorem.  

Bartosz Kwasniewski (Odense) will give a talk with title: Paradoxicality and pure infiniteness of  C*-algebras associated to Fell bundles

Abstract: Abstract: In this talk we present conditions implying  pure infiniteness of the reduced cross-sectional $C^*$-algebra $C^*_r(\mathcal{B})$ of a Fell bundle $\mathcal{B}$ over a discrete group $G$. We introduce notions of aperiodicity, $\mathcal{B}$-paradoxicality and  residual $\mathcal{B}$-infiniteness.  We discuss their relationship with similar conditions studied, in the context of crossed products, by the following duos: Laca, Spielberg; Jolissaint, Robertson; Sierakowski, R{\o}rdam;  Giordano, Sierakowski and Kirchberg, Sierakowski.    (based on  joint work with Wojciech Szyma{\'n}ski)