Hagen KleinertI collaborated with Feynman and wrote a paper with him which led to the most accurate theory of critical exponents so far.
The prediction was confirmed in a satellite experiment by Lipa et al., published under the title "Specific heat of liquid helium in zero gravity very near the lambda point" in Phys. Rev. B 68, 174518 (2003).
Since I had to
tell the story repeatedly, most recently for the French edition of Science,
I have set up a web page with all the info:
Institut fuer Theoretische Physik
Freie Universitaet Berlin