Carissimi, 

riprendono dopo la lunga pausa i seminari di Algebra, Topologia e Combinatoria. Trovate di seguito l'avviso per l'appuntamento di questa settimana.

Cari saluti, 

Filippo

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Giovedì 16 aprile, ore 16:00-18:00​

Benjamin Collas (Bayreuth Universität)

Titolo:

Arithmetic of inertia in braids groups and Grothendieck-Teichmüller theory.

Abstract:

Following Grothendieck's "Esquisse d'un programme", Grothendieck-Teichmüller theory is the study of the absolute Galois group of rational through combinatorial properties of the moduli spaces of curves M_{g,n}. Originally developed by Drinfel'd and Ihara in the context of quantum groups and arithmetic geometry, it is guided by the existence a certain stratification of the space which then translates in term of inertia when considered from the fundamental group point of view.

We will present the main ideas of a Grothendieck-Teichmüller theory by considering first the case of curves of genus zero and its relation with the Artin braid groups -- all the needed notions will be given in detail within the case of M_{0,4}.  By then considering the Artin braid groups as a special case of generalized braid groups, we will explain how these ideas can be adapted, and may lead to a similar ``Grothendieck-Dynkin'' theory, when studying the geometry of the wonderful model compactification of hyperplane arrangements.

Il seminario sarà diviso in due parti di 45' ciascuna.​

Giovedì 30 Aprile 2015, ore 16:00-18:00​

Lewis Topley (Università di Padova)

TBA