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Geometry-Topology Seminar

Tuesday, December 14, 2021 - 5:15pm

Jennifer Hom

Georgia Tech


University of Pennsylvania

via Zoom

The Zoom link will be sent by e-mail to faculty and students at UPenn, and for others can be obtained by e-mailing After the talk, we will stay online for a while for a social visit, with the recording turned off.

The unknotting number of a knot is the minimum number of crossing changes needed to untie the knot. It is one of the simplest knot invariants to define, yet remains notoriously difficult to compute. We will survey some basic knot theory invariants and constructions, including the satellite knot construction, a straightforward way to build new families of knots. We will give a lower bound on the unknotting number of certain satellites using knot Floer homology. This is joint work in progress with Tye Lidman and JungHwan Park.