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Speaker:

Grigori Avramidi
Affiliation:

MPIM
Date:

Mon, 22/04/2024 - 14:00 - 15:00
Location:

MPIM Lecture Hall
Parent event:

MPIM Topology Seminar In the 60's Cohn showed that all ideals in the group algebra of a free group are free. Bass and Wall used this result to show that all two-dimensional complexes with free fundamental groups are standard: they are all homotopy equivalent to wedges of circles and 2-spheres. The goal of this talk is to describe recent results of this type for groups acting on hyperbolic spaces. I will discuss an algorithm showing that in the group algebra of a group acting on a hyperbolic space, ideals generated by ``few'' elements are free (where "few'' is a function of the minimal displacement of the action) and an application to complexity of cell decompositions of hyperbolic manifolds. Joint work with Thomas Delzant.

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