Concordance in homology cobordisms

Concordance in homology cobordisms

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Tye Lidman, North Carolina State University
Fine Hall 314

Not all knots bound a disk in the three-sphere, but they do always bound a PL disk in the four-ball.  It turns out that this fails for knots in arbitrary homology spheres.  We study a group that measures this failure and show that it is infinitely-generated.  This is joint work with Jen Hom and Adam Levine.