Virtual Seminar on

Geometry and Topology

How to join

Zoom Meeting ID 739-035-2844

Password Zero minus the Euler characteristic of a closed oriented surface of genus 4000

Time Wed 4 pm or Thursday 9 am (or so) in KST (Korea Standard Time)


December 2 (Th) 9 - 10 am Korea

Minju Lee (IAS)



November 3 (W) 10 - 11 am Korea

Hongbin Sun (Rutgers University)

All finitely generated 3-manifold groups are Grothendieck rigid

A finitely generated residually finite group G is said to be Grothendieck rigid if for any finitely generated proper subgroup H<G, the inclusion induced homomorphism \hat{H}\to \hat{G} on their profinite completions is not an isomorphism. There do exist finitely presented groups that are not Grothendieck rigid. We will prove that, if we restrict to the family of finitely generated 3-manifold groups, then all these groups are Grothendieck rigid. The proof relies on a precise description on non-separable subgroups of 3-manifold groups.

October 13 (W) 4 - 5 pm Korea

Javier de la Nuez González (KIAS)

Title: Formal solutions and their role in the study of the first order theory of free groups

Abstract: I will discuss the existence of formal solutions for positive and related sentences valid in free groups. I will also hint at their role in Sela's solution to the Tarski problem, together with that of other tools.


Harry Hyungryul Baik (KAIST)

Sam Sang-hyun Kim (KIAS)

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