Date: 6 March 2020 Location: Hempfield High School, Room 213 Speaker: Michael McCooey, Franklin and Marshall College Title: On a counterexample to a theorem of McCooey, and other stories Abstract: I will begin with a short introduction to the parts of my research that apply equivariant cohomology to study which finite groups can admit actions of certain four-manifolds. While some in the audience will have seen this before, I will start with basic examples. I will then relate the sad story of the discovery by Semra Pamruk of an error in my claim of a collapsing result for a certain spectral sequence, and discuss her recent work with Ian Hambleton on a result which, though weaker, has the virtue of being correct. Time permitting, I will discuss some of my other recent research towards developing a better geometric understanding of the differentials in that spectral sequence in terms of equivariant characteristic classes and the Atiyah-Bott integration formula.