This evening’s Hollywood-style entertainment came from the Perimeter Institute, where they had a big public event, live-streamed to the world, featuring Nima Arkani-Hamed speaking on Quantum Mechanics and Spacetime in the 21st Century. You should be able to watch the thing soon from the Perimeter site, should be posted at some point here.
The talk was pretty much the same as many other such Arkani-Hamed talks, quite close to the one at the IAS nearly four years ago, discussed here. In this format he can’t go on forever, was cut off by around an hour and a half, so said he couldn’t get to the third part of the talk, which might have been the 21st century part (amplituhedron?). As in the IAS talk, what he did cover was first mostly the 1960s sort of arguments that Weinberg describes in the first volume of his textbook about the constraints on consistent relativistic QFTs. Then an advertisement for the Veneziano model and string theory. The last part of the talk was a long advertisement for SUSY, ending with an acknowledgement that it wasn’t showing up at the LHC. He’s now giving 2018 as the date for when we’ll know about LHC-scale SUSY, which is moved up from the 2020 of the IAS talk of 2011, but still very different than the “year or so after LHC startup” he was saying in 2005. The current plan is for maybe 10 inverse-fb next year, 50 in 2016. If nothing shows up then, I don’t see that the next 50-100 supposedly coming by 2018 have any real chance of finding SUSY.
One thing that struck me about the talk was its odd combination of over-the-top enthusiasm (“this is the greatest time ever!”) and intense defensiveness. He kept emphasizing the claim that theorists, even without experiment to keep them honest, were working with highly constrained rules, that it was very hard to do anything not obviously wrong. He denied sociology had to do with what unsuccessful ideas people decide to pursue. He didn’t address at all the “not even wrong” problem: what about the things like the landscape, baroque constructions that evade being wrong by being empty? I like a lot this picture and quote from Perimeter:
If you manage to find one idea that’s not obviously wrong, it’s a big accomplishment. Now, that’s not to say it’s right. But not obviously being wrong is already a huge accomplishment in this field.
I think the defensiveness here that’s coming through is very personal. He’s gotten a $3 million award and a reputation as a leader of the field for ideas that haven’t worked out, but which he can defend as “not obviously wrong” and thus a “huge accomplishment”.
All in all, the talk was very backward looking, recapitulating the SUSY/string theory ideology that has led us to where we are. It looks like he’s planning on hanging in until 2018 with the same story, only then maybe admitting failure (and possibly going for “the multiverse did it, we never had a chance” cop-out). He did end with an upbeat claim that the SUSY picture being all wrong would be very exciting, opening up the field by showing we need something completely new. The obvious question for him is “you pretty clearly wouldn’t now bet $10 on SUSY at the LHC, so why wait?” Why not stop giving promotional talks about SUSY? One thing he could have done that would have generated some excitement in the field would be to have pitched out the two-thirds of the talk he did give, publicly saying these ideas aren’t working, and talked about something from this century, amplitudes or whatever, the part of the talk he never got to.
Well, maybe in 2018…
Update: You can watch the talk here, along with some online commentary in a chat box that was rolling during the talk.
Update: There was also a more technical talk at Perimeter by Arkani-Hamed, earlier in the day, on Cosmological Collider Physics. The video doesn’t seem to be available yet though.
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