## Wednesday, November 30, 2005 ... //

### Computation after 90th birthday

We just had a dinner to celebrate the Loeb lecturer, John Hopfield from Princeton, who bravely applies physical reasoning to neural networks and other models of the human brain.

There have been many interesting discussions during the dinner but I will only mention a couple of them. Howard Georgi allowed me to understand a bit better the pretty high score of our F-group in the last homework problem set assigned in my class. Thanks, Howard, for the help. ;-) Yes, F stands for "female". Two different homework assignments have been made for the two groups, and no one has yet called the New York Times, not even Howard himself. ;-)

Incidentally, my feeling after the class in the morning was that 160 minutes is simply too little to properly teach scattering, partial wave analysis including all of its limiting cases, Born approximation, including all the kinematical relations between amplitudes, cross sections, transition rates, time-dependent perturbation theory, and examples including the Yukawa and Coulomb potentials, spherical well, and 38 other issues. Moreover, these calculations in the old-fashioned quantum mechanics are sometimes even messier than in quantum field theory. I would probably reduce the amount of material related to these questions in the syllabus.

Tai Wu, a member of our band, joined my opinions about the Summers controversy and Noam Chomsky and other things. We chatted about the LHC, too. And no, C.S. Wu did not belong to his family.

Ursula Holliger (harp) described many things including the music critics. Of course, they're often annoying and they became critics because they could not become the musicians. Not surprisingly, the very same thing probably holds for the literary critics and the physics critics, too. ;-)

Chris Stubbs has finished reading Barton Zwiebach's book on string theory. Because he learned many things and was pleasantly surprised that the whole modern high energy theoretical physics is fully accessible to him, he actually thinks that every experimental physicist should learn string theory from this book. I am happy to report this experimental conclusion. :-)

Incidentally, Chu Xing who works in a factory in Hong Kong also studies Barton's book. Sometimes, he would find it helpful to know the answers to Barton's problems in the book; he informed me in the e-mail. When I had the pleasure to talk to Dr. Simon Capelin who may be credited for having published so many great physics books in the Cambridge University Press today in the afternoon, he agreed that Chu Xing should get the password to access the web page of Barton's book at the CUP's server. We will see this week whether Barton will agree. ;-) Good luck, Chu.

One of the crimes against the copyright (not humankind) I did in 1993 was to ask a librarian in Prague to xerox the superstring textbook by Green, Schwarz, and Witten for me. She did so! For 12 years, I could not sleep because I worried that the Cambridge University Press would eventually sue me. It turned out today that Dr. Capelin who published the book will probably forgive me this particular sin!

Norman Ramsey has told me many stories about the history of physics, his lectures on 9/11/2001 (the day of my PhD defense), the development of atomic clocks, negative temperatures of lasers, the most precise current experiments testing both special and general relativity, and his recent studies of string theory. He believes that the vacuum energy is gonna be an important question in physics for the years to come. Another very illuminating comment from him was about the changes of your approach to research when you're older than 90 years. Of course, when you're above 90, almost everything works easier than before. Just the short-term memory is slightly worse. When you need to finish some integral - that you otherwise do on the top of your head - with your calculator, it is sometimes a bit more difficult to remember what you want to type on your calculator. It is slightly more difficult than when you are young, e.g. about 85 years or so.

Well, what an impressive person. ;-)

In the afternoon, James Wells (Michigan) was explaining his children GUT constructions extending NMSSM but I will only mention the talk if I have really too much time tomorrow which is unlikely.