There’s a great profile of Nima Arkani-Hamed by Natalie Wolchover just out at Quanta magazine, under the title Visions of Future Physics. I recently linked to another profile of him from the IAS, which covers some similar ground.
He’s often been a topic of postings here, and the profile explains why, with his colleagues describing him as the “messiah”, “Pied Piper” and “impresario” of high energy physics.
“He keeps coming up with the goods, and his persuasiveness is hypnotic,” said Raman Sundrum, a theoretical physicist at the University of Maryland in College Park, “so a lot of people follow where he leads.”
I’ve often marveled at his performances, with his talks sometimes a unique mixture of brilliance, insight, and over-the-top outrageous indefensible claims (his talk here last week was uncharacteristically restrained). As an example of the genre, the IAS profile includes:
“It is extremely interesting to think about getting sophomores up to the speed of a second-year graduate student. I think it is possible,” says Arkani- Hamed.
which is simultaneously quite inspirational and, well, nuts.
A couple years ago I was struck by a talk of his in which he showed a lot of self-knowledge, describing himself as an “ideolog” (see here). There’s more about this in the Quanta profile:
“It’s important for me while I’m working on something to be very ideological about it. And then, of course, it’s also important after you are done to forget the ideology and move on to another one.”
The ideologies on display this time include a very speculative picture of a future union of mathematics and theoretical physics:
Ultimately, he said, anywhere from 10 to 500 years from now, the amplituhedron and these cosmological patterns will merge and become part of a single, spectacular mathematical structure that describes the entire past, present and future of everything “in some timeless, autonomous way.”…
There is a mathematical proof, Arkani-Hamed observed, that all algebraic numbers can be derived from configurations of a finite whole number of intersecting points and lines. And with that, he expressed a final conjecture, at the end of a long, cerebral day, before everyone else went home to bed and Arkani-Hamed headed to the airport: Everything — irrational numbers, along with particle interactions and the correlations between stars — ultimately arises from possible combinatorial arrangements of whole numbers: 1, 2, 3 and so on. They exist, he said, and so must everything else.
Personally, I don’t think this is going to work out, but he’s right that people need a vision to pursue, to drive them forward in finding new things. Unless he gets a lot further with it, I don’t think this one is going to get so much interest as to drive out other ideas, especially from mathematicians interested in physics, who have other competing visions.
Where Arkani-Hamed has become a really problematic ideolog, one endangering the health of the subject, is in his insistence on “naturalness” as the central question of HEP theory at the TeV scale, coupled with the ideology that if the LHC doesn’t see new “natural” physics at the TeV scale, then the intellectual suicide of the multiverse is all HEP theory has to look forward to. He’s been pushing this ideology, hard, for quite a while now, and I think it’s long past time for him to take his own advice and “forget the ideology and move on to another one.”
Much of the article is about his efforts to push forward a Chinese plan to build a next-generation collider. Perhaps his great enthusiasm will help move this project along (a book about it by Yau and Nadis, From the Great Wall to the Great Collider, will soon come out). It raises all sorts of difficult issues for the future of experimental HEP, including that of the future of CERN, issues that will play out over many years (timelines for things like this are generally wildly over-optimistic, and here people are talking about 2042). Framing the case for a 100 TeV machine as “1% fine-tuning evidence for the multiverse from the LHC wasn’t convincing, even though we said it would be, so we need a bigger machine to get .1% fine-tuning evidence” is something that I think isn’t going to fly, no matter how enthusiastically presented. In the article Kyle Cranmer makes the point that .1% tuning versus 1% tuning means little:
“I am very sympathetic to the idea that this is a critical point in the field and that naturalness/fine-tuning is a deep issue,” he wrote in an email. “However, I’m not convinced that if we built a 100-TeV collider and saw nothing that it would be conclusive evidence that nature is fine-tuned.” There would remain the nagging possibility that a natural completion of the Standard Model exists that a collider simply can’t access.
argues that if no new particles are found at 100 TeV, this will leave physicists exactly where they are now in their search for a more complete theory of nature — clueless.
I think David Gross has it right:
Gross, who considers naturalness a murky concept, simply wants a last-ditch search for new physics. “We need more hints from nature,” he said. “She’s got to tell us where to go.”
The case for mankind to embark on a new project to push forward the boundaries of science is the same as it has always been: even though it’s expensive and difficult, we should do it because we’ll see how the world works at an even smaller distance scale. Just possibly we’ll learn enough to understand how to improve the Standard Model and achieve an even deeper insight into the physical universe.
Update: Gross and Witten have an editorial today in the Wall Street Journal (as usual with the WSJ, try Googling the article to get around their paywall), supporting the idea of a Chinese Great Collider project.