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Heike Harenbrock

Mittagsseminar zur Arithmetik: Catrin Mair (Münster): What are condensed contractible schemes ... (Talk 2): and why Spec(Z) is not?

Tuesday, 12.05.2026 10:15 im Raum SRZ 216/217

Mathematik und Informatik

Condensed Mathematics is a relatively new approach to topology that facilitates working with algebraic structures equipped with a topology. In homotopy theory, we study all kinds of spaces using algebraic invariants, which are very often naturally endowed with a topology. In my first talk, I will introduce you to the world of condensed mathematics in the context of homotopy theory. I will explain the notion of a condensed homotopy type and how it is defined in the case of schemes. I will provide an overview of the information encoded in this invariant and in what sense it refines more classical invariants such as the étale homotopy type or the pro-étale fundamental group. My focus will be on the question of when a scheme is (not) condensed contractible, i.e., its condensed homotopy is (not) contractible. In my second talk, I will continue the study of condensed contractible schemes. The main goal will be to compute the condensed fundamental group of a Dedekind ring. More specifically, we will see that the scheme Spec(Z) is not condensed contractible, even though it is étale-contractible. This talk is based on joint work with Haine, Holzschuh, Lara, Martini, and Wolf, as well as on extended results from my dissertation.



Angelegt am 07.05.2026 von Heike Harenbrock
Geändert am 07.05.2026 von Heike Harenbrock
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