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November 22, 2007
So Long, Sidney
After a long illness, Sidney Coleman passed away this week. I last saw him 2 1/2 years ago, and, even then, the toll his disease had taken was rather painful to see.
In his heyday, he was a figure to be reckoned-with. Few understood physics more deeply and none could explain it more lucidly. But it was his (mostly self-deprecating) wit that endeared him to us all. Luboš Motl’s now-classic photo:
captures the spirit of the Sidney we all remember. I learned a tremendous amount from my erstwhile Adviser. The world of Physics — my world — is poorer without him.
There are some lovely reminiscences at Betsy Devine’s and at CosmicVariance.
November 21, 2007
A Little Group Theory …
I really wasn’t going to post about Garrett Lisi’s paper. Preparing a post like this requires work and, in this case, the effort expended would be vastly incommensurate with any benefit to be gained.
So I gritted my teeth through a series of credulous posts in the Physics blogosphere and the ensuing media frenzy. (Yes, Virginia, science reporters do read blogs. And if you think something is worth posting about, there’s a good chance — especially if it has the phrase “Theory of Everything” in the title — they will conclude that it’s worth writing about, too.) But, finally, it was Sean Carroll’s post that pushed me over the edge. Unlike the others, Sean freely admitted that he hadn’t actually read Lisi’s paper, but decided it was OK to post about it anyway.
So here goes.
I’m not going to talk about spin-statistics, or the Coleman-Mandula Theorem, or any of the Physics issues that could render Garrett’s idea a non-starter. Instead, I will confine myself to a narrow question in group representation theory. This has the advantage that
- It’s readily decidable, on purely mathematical grounds.
- Since it involves the starting point of Garrett’s analysis, a negative answer would render all of the other questions moot.
November 14, 2007
S-Duality for N=2
You’ve probably noticed a lot of recent activity centered around S-duality for N=4 supersymmetric gauge theories (hint: it goes by the name of “Geometric Langlands”). There are, similarly, finite N=2 supersymmetric gauge theories, for instance with hypermultiplets in the fundamental. One might ask whether some notion of S-duality holds for them as well. For a few, there is such a notion, but, in most cases, the construction of a dual theory has been elusive, and the answer cannot be as simple as in the N=4 case.
November 13, 2007
Leopard
Now that everyone else has written theirs, and any vestigial interest in postings about Apple’s new Operating System has died down, I guess it’s safe for me to trot out my own notes on upgrading to Leopard.
First, I should refer you to John Siracusa’s excellent, and most comprehensive review. I’ll try to avoid repeating his comments, and concentrate on my own, more idiosyncratic observations.