Upsilon invariant for graphs and homology cobordism group of homology cylinders
Akram AlishahiAGDT Seminar
on 2/18/22
Abstract: We construct an example of a cork that remains exotic after taking a connected sum with S^2×S^2. Combined with a work of Akbulut-Ruberman, this implies the existence of an exotic pair of contractible 4-manifolds which remains absolutely exotic after taking a connected sum with S^2 × S^2.