FYI.

I plan to attend; if anyone needs a ride, let me know.

William H. "Bus" Jaco Regents Professor, Grayce B. Kerr Chair, and Head Department of Mathematics

---------- Forwarded message ---------- From: Rubin, Leonard R. lrubin@ou.edu Date: Tue, Jan 16, 2018 at 12:48 PM Subject: talk on Dehn-Kneser To: "william.jaco@okstate.edu" william.jaco@okstate.edu Cc: "rowe@mathematik.uni-mainz.de" rowe@mathematik.uni-mainz.de, "Forester, Max B." mf@ou.edu

Bus: I just noticed on your math website that you are getting a very nice award of recognition from your department. My congratulations.

I wanted to call your attention to a talk that will be given here in our topology seminar on Wednesday, February 14 (see attached). David Rowe has been studying correspondence that had occurred between Kneser and Dehn I guess around 1929. It was at this time that Kneser had discovered a huge gap in Dehn’s proof of what we call Dehn’s lemma. David is going to talk about this. We are getting a great scoop because he has been invited by Cameron Gordon to speak at the UT colloquium in March on this very same topic.

I hope that you and some of your colleagues would be able to attend. Our seminar usually begins at 3:45, but often when we have an outside speaker, it starts at 4:00, leaving time before it to have tea and cookies. The actual schedule has not yet been set. I kind of suggested to David that this might be a little less formal and a little bit free-form in the sense that some people might be there who could say at least a little bit about how and why such a lemma has an impact on the topology of 3-manifolds. It would be of interest to say something about why the loop theorem is superior to Dehn’s lemma (I do not know these things), which I found out by having a glance at John Hempel’s book.

OK, so let me know what you think about all this. I certainly hope that you and others can attend. As usual, we would go out for dinner after the talk.

Lenny