Geometry Seminar
Winter 2022
Thursdays 3:304:30pm in Eckhart 202

 Thursday February 17 at 3:30PM4:30PM in Eckhart 202
 Maggie Miller, Stanford University
 Building concordances

Abstract: I'll talk about one of my favorite theorems in 4dimensional topology (or at least its implications), in which Hirose shows exactly which automorphisms of a genusg surface can be achieved by smooth ambient isotopy in S^4 of an unknotted surface. This theorem is surprisingly useful, e.g. it can be used to reprove Kervaire's theorem that every smooth 2sphere in S^4 bounds a smooth 3ball into B^5 (my actual favorite theorem) with extra conditions on the embedding that Kervaire's argument does not achieve. I'll also show how to make use of these theorems to actually construct the knotted handlebodies that I'll describe on Wednesday in the colloquium..

 Thursday February 24 at 3:30PM4:30PM in Eckhart 202
 Bena Tshishiku, Brown University
 Convex cocompact subgroups of the Goeritz group

Abstract: This talk is about hyperbolicity of surface group extensions and a question of FarbMosher about whether purely pseudoAnosov subgroups of mapping class groups are convex cocompact. I will explain this problem and give an answer for subgroups of the genus2 Goeritz group, which is the group of mapping classes of a genus2 surface that extend to the genus2 Heegaard splitting of the 3sphere.
Due to the high number of requests, we are no longer accepting speakers via selfinvitations.
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