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December 13, 2003

Historical Contingency

Thomas Dent’s comment on my previous post reminded me of an anecdote.

Several years ago, I was sitting in the CERN cafeteria, chatting with a phenomenologist colleague. I opined that it was, on balance, a very good thing that the then-recent advances in our understanding strongly-coupled supersymmetric gauge theories had not come a decade earlier. “Why so?” asked my friend. “Because,” I replied, “if we’d known all the stuff in the early '80s, the community would have wasted the intervening decade applying that knowledge to building elaborate models of extended technicolour. Instead, we poured our efforts into developing string theory.” At this, my friend grew very agitated. “But you don’t understand!” he spluttered, “There are so many more possibilities for constructing models now.”

Indeed …

Posted by distler at December 13, 2003 12:16 AM

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Re: Historical Contingency

Indeed, today it’s a model builders dream becoming true ! We already had all these nice things like SU(5), SO(10), E6 grand unification, left-right symnmetric models, Pati-Salam models, flipped SU(5) models, all with minimal or non-minimal Higgs sector, then composite models incl technicolor, plus supersymmetry and then a mixture of all of that !

However, after 25 years of model building, things almost seemed to have gotten boring - but fortunately, we now have extra dimensions at our disposal - we can now repeat all of this but now in 5 and 6 dimensions ! We have already gratefully seen papers on SO(10) GUTs in 6d (hep-ph/0108071), and surely if we wait a bit longer, there will be even more variants…it’s going forward all the time ! And even better: not only extra dimensions and orbifolds but also branes — we can now cook mixtures of all of that, and differently so on various branes as well, we can distribute susy breaking, chiral fermions, FI terms here, just as we please — possibilities abound! The rate of new models is skyrocketting again, proving that this field is indeed one of the most productive ones.

And the best thing of all is that we even don’t need any more learn complicated stuff like gravity, or string theory, to tackle such grounds… we are finally free of any consistency contraints, we do not need to understand non-perturbative properties, it’s just the idea what counts, and the crazier the more exciting !

Posted by: An excited model builder on December 13, 2003 12:51 PM | Permalink | Reply to this

Re: Historical Contingency

I suspect ‘Excited model builder’ of a degree of insincerity…

Mike Duff always used to remind me that Joe Polchinski gave a talk on D-branes in 1991, whereupon everyone ignored them for 4 years. If D-branes had come on the scene in ‘91 the Maldacena Conjecture would have been called something quite different…

But I don’t think model-building would have changed very much. Model-builders like what is simple and easy-to-calculate and connects with data: when LEP was running, minimal SUSY was always on top in these departments. Current trends are due to the lack of data, Higgses and superpartners.

Maybe it would be a good idea to ignore all models of the Higgs, electroweak symmetry-breaking and the hierarchy until the LHC is turned on.

But then, 1/3 of the model-building industry is built on showing that the models of the other 1/3 don’t work. (The remaining 1/3 work on neutrinos, so their models are all ruled out by data.) With any luck they will cancel out and we will get to 2007 with only one or two models left. (Some hope.)

Posted by: Thomas Dent on December 16, 2003 6:12 AM | Permalink | Reply to this

Re: Historical Contingency

Yeah, I detected a note of sarcasm in Excited’s comment, too.

I’m actually pleased that Murayama (and others) are pushing the envelope a bit, in terms of what might be seen at LHC. Both from a theorist’s point of view, and from an experimentalist’s (they need to know what to look for and where to put their cuts), it’s important to explore alternatives to the (MS)SM even before the LHC turns on.

Posted by: Jacques Distler on December 16, 2003 9:45 AM | Permalink | Reply to this

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