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November 17, 2016
Thursday, November 17
Homotopy Theory
Time: 13:00
Speaker: Marco Vergura (Western)
Title: "Complete Segal Spaces"
Room: MC 107

Abstract: We will introduce Complete Segal spaces and prove they describe an equivalent homotopy theory to the one of quasi-categories.

Colloquium
Time: 15:30
Speaker: Pierre Guillot (Strasbourg)
Title: "Massey products and Galois cohomology"
Room: MC 107

Abstract: Massey products are, originally, operations defined in the context of algebraic topology, on cohomology rings. However, when one specializes to group cohomology, work of Dwyer shows that the study of these operations amounts to that of elementary extension problems, involving the group of unipotent matrices over a finite field. When we specialize further, and consider Galois groups in particular, an ambitious conjecture predicts that Massey products always vanish. This has been actually proved for triple Massey products, in complete generality. In this talk, I will describe joint work with Minac, Tan, Topaz and Wittenberg, showing that the conjecture is true for fourfold Massey products in the cohomology of number fields.