Mathematician Per Enflo, who solved a huge chunk of the 'invariant subspaces problem' decades ago, may have just finished his work.This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights. Nathan Brownlowe, Senior Lecturer in the School of Mathematics and Statistics at the University of Sydney. Two weeks ago, a modest-looking paper was uploaded to the arXiv preprint server with the unassuming title "On the invariant subspace problem in Hilbert spaces". The paper is just 13 pages long and its list of references contains only a single entry. The paper...