Logic Seminar

Mark SchachnerCornell University
Whitehead's problem for countable groups

Monday, October 16, 2023 - 2:55pm
Malott 205

Following work due to Jeffrey Bergfalk, Chris Lambie-Hanson, and Jan Saroch, we exposit proofs related to the countable and torsion cases of Whitehead's problem. In particular, we prove the nonvanishing of Ext groups for countable, torsion-free, nonfree abelian groups, as well as for arbitrary abelian groups with torsion.