George Mackey, mathematician

Mackey worked on dual topologies on vector spaces and their duals before taking up the task of helping to edit the papers of J. von Neumann after the latter's death. One of the results attributed to von Neumann (by Wigner) was that the very important analysis by Wigner of the complete set of irreducible unitary representations of the Poincaré group can be made completely rigorous. Mackey told me that he did not find a proof of this among von Neumann's unpublished papers, but there was only a sketch which omitted the crucial step. This led to Mackey's second great contribution to mathematics, which is at the foundation of relativistic quantum mechanics: the Mackey theory of unitary representations of groups.

I met Mackey in 1965 while I was a research associate of Irving Segal and I attended Mackey's famous lectures on group theory. Barry Simon was also in the audience.