Comments on: Coleman Conference http://www.math.columbia.edu/~woit/wordpress/?p=171 Tue, 24 Nov 2009 05:18:29 -0500 http://wordpress.org/?v=2.8.6 hourly 1 By: Not Even Wrong » Blog Archive » Sidney Coleman 1937-2007 http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-30730 Not Even Wrong » Blog Archive » Sidney Coleman 1937-2007 Mon, 19 Nov 2007 22:43:54 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-30730 [...] at the age of seventy. Coleman had been in quite poor health in recent years. I wrote about him here back in 2005, after attending a conference held at Harvard in his [...] [...] at the age of seventy. Coleman had been in quite poor health in recent years. I wrote about him here back in 2005, after attending a conference held at Harvard in his [...]

]]> By: Anonymous http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2793 Anonymous Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2793 Maybe I am missing something, but how can QCD be dual to a gravitational theory in AdS_5 when it doesn't have a massless spin-2 particle? Isn't that the same problem which killed string theory as a dual theory to QCD? The absence of a massless spin-2 particle? Or perhaps the graviton IS a QCD bound state? That would be shocking! But I guess if you don't have a Planck brane... Maybe I am missing something, but how can QCD be dual to a gravitational theory in AdS_5 when it doesn’t have a massless spin-2 particle?

Isn’t that the same problem which killed string theory as a dual theory to QCD? The absence of a massless spin-2 particle?

Or perhaps the graviton IS a QCD bound state? That would be shocking!

But I guess if you don’t have a Planck brane…

]]> By: Anonymous http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2794 Anonymous Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2794 I want to talk about Sidney Coleman. I met him almost 25 years ago. I was a 1st year grad student. He struck me as an "old" man. Now I know that he couldn't have been older than 45. Unlike the rest of the Harvard "superstars", he was not arrogant, he was not patronizing, and he was not abnoxious. He was approachable, and he very patiently listened to questions, then very kindly answered them. Sometimes his answer was an honest "I vaguely know these things. I'm not an expert". In those days, there was a joke circulating around the physics dept at Harvard (I think it's attributed to Claude Bernard who was a grad student of Weinberg's at the time): "How do you do physics at Harvard? You go to Witten to give you a problem to work on. You go to Coleman to tell you how to solve it. Then you go to Weinberg to write you a reference letter." I'm saddened by his illness, and by the fact that he can longer teach physics and discuss physics. I want to talk about Sidney Coleman. I met him almost 25 years ago. I was a 1st year grad student. He struck me as an “old” man. Now I know that he couldn’t have been older than 45.

Unlike the rest of the Harvard “superstars”, he was not arrogant, he was not patronizing, and he was not abnoxious. He was approachable, and he very patiently listened to questions, then very kindly answered them. Sometimes his answer was an honest “I vaguely know these things. I’m not an expert”.

In those days, there was a joke circulating around the physics dept at Harvard (I think it’s attributed to Claude Bernard who was a grad student of Weinberg’s at the time):

“How do you do physics at Harvard? You go to Witten to give you a problem to work on. You go to Coleman to tell you how to solve it. Then you go to Weinberg to write you a reference letter.”

I’m saddened by his illness, and by the fact that he can longer teach physics and discuss physics.

]]> By: Arun http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2795 Arun Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2795 "That's only possible for massive particles and the theorem doesn't apply." I thought the purpose of the theorem was to rule out massless bound states; not to assume that all bound states are massive. Anyway, I'm probably missing the point. “That’s only possible for massive particles and the theorem doesn’t apply.”

I thought the purpose of the theorem was to rule out massless bound states; not to assume that all bound states are massive. Anyway, I’m probably missing the point.

]]> By: Johan http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2796 Johan Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2796 Regarding the "gravity as a gauge theory" issue, Deser's bootstrap approach does give you the Einstein-Hilbert action but I believe it only works for spacetimes that are topologically R^4. Penrose has shown that there is no map from Schwarzschild spacetime to Minkowski spacetime that takes lightcones into lightcones, which jives well with the Witten-Weinberg argument. Regarding the “gravity as a gauge theory” issue, Deser’s bootstrap approach does give you the Einstein-Hilbert action but I believe it only works for spacetimes that are topologically R^4. Penrose has shown that there is no map from Schwarzschild spacetime to Minkowski spacetime that takes lightcones into lightcones, which jives well with the Witten-Weinberg argument.

]]> By: Anonymous http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2797 Anonymous Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2797 P.S. you're describing a topological quantum field theory. P.S. you’re describing a topological quantum field theory.

]]> By: Anonymous http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2798 Anonymous Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2798 That's only possible for massive particles and the theorem doesn't apply. That’s only possible for massive particles and the theorem doesn’t apply.

]]> By: Arun http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2799 Arun Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2799 Probably a dumb question, but what happens to the Witten-Weinberg theorem if the particular QFT admits of no single-particle states except on length scales very much smaller than the natural scale of the theory? Probably a dumb question, but what happens to the Witten-Weinberg theorem if the particular QFT admits of no single-particle states except on length scales very much smaller than the natural scale of the theory?

]]> By: Peter http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2800 Peter Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2800 No, Lee Smolin wasn't there. But a message from him was read at some point I recall. No, Lee Smolin wasn’t there. But a message from him was read at some point I recall.

]]> By: Anonymous http://www.math.columbia.edu/~woit/wordpress/?p=171&cpage=1#comment-2801 Anonymous Wed, 31 Dec 1969 19:00:00 +0000 http://www.math.columbia.edu/~woit/wordpress/?p=171#comment-2801 Peter, was Lee Smolin there for this conference since he was Coleman's graduate student? Peter, was Lee Smolin there for this conference since he
was Coleman’s graduate student?

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