### 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
## 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 !