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Interesting if fruitful
james_nicoll


Physicists have discovered a jewel-like geometric object that dramatically simplifies calculations of particle interactions and challenges the notion that space and time are fundamental components of reality.

Also posted at Dreamwidth, where there are comment count unavailable comment(s); comment here or there.

I only vaguely understand what they're going on about here, but it apparently has to do with a supersymmetric Yang-Mills theory which is a few steps removed from anything realistic. Still, the techniques sound really interesting.

...To put that in slightly less abstruse language, that's a quantum theory in which the stuff in the world consists only of some particles analogous to gluons, and various particles which are (unobserved in reality) counterparts of the gluons that have different spin, with special symmetries under exchange of the gluons with their partners.

It's a popular toy theory to play with because it's not so simplified as to be completely trivial, but it has various nice mathematical properties that make it more tractable than realistic theories.

It has some relationship to N=8 Supergravity, of which there are indications it's also finite. Or so I gather as a non-physicist.

http://www.math.columbia.edu/~woit/wordpress/?p=268

http://physics.aps.org/articles/v2/70

...And furthermore they're apparently talking about the _planar limit_ of that theory, which I _think_ is the limit of a very large number of gluon colors (making it even less realistic).


Edited at 2013-09-21 12:37 pm (UTC)

Some comments on this at Not Even Wrong. Despite the name of that blog, it's not entirely critical.

Edited at 2013-09-20 03:58 am (UTC)

Woit and Lubos Motl are both positively interested; this may be a first.

"A non-expert proposes that all experts have missed something obvious, discovered something that experts would have to be stupid to have missed. Again. Like all the other top articles on our site. Look! We have perpetual motion and word salad. Autism."

Actually, Nima Arkani-Hamed is a pretty big name in the field, and most of what I've heard from actual experts about the work is positive. The article is, however, glossing over a whole lot of qualifications about how far removed this is from effortlessly solving the Standard Model. It seems to be a beautiful result in an illuminating but unrealistic toy model (though less unrealistic than some).

"a 'science' article proposes that all experts have missed something obvious, and discovered something that experts would have to be stupid to have missed. Again. And this is still posted on a site where the rest of the articles appear cracked"

Better?

That site still does not fill me with confidence, and the credibility of the source is still a major factor for me when considering "everything the EXPERTS know is STUPID" claims.

But who doesn't love a simplifying model? :)

I don't see why they'd have to be stupid to have missed a very different approach that requires all sorts of specialised maths not normally associated with quantum physics.

And is inspired by experimental data from the mid-2000s.

No, not better at all. Where is it proposed that they missed something obvious? Doesn't say anything about "the experts have to be stupid", either. You're completely misreading the article.

Edited at 2013-09-20 11:19 am (UTC)

It is frustratingly hypey, though. Part of the problem is that what it's describing--an unusual method for calculating scattering amplitudes in a certain quantum field theory--is so abstract that actually speaking sensibly about it for a lay audience would be difficult.

The analogy that occurred to me was the discovery of calculus after centuries of computing areas by the method of exhaustion...but that's only going to fly for a select subset of 'lay audience.'

And we all know that such beautiful results never get absorbed into later physics in unexpected ways... I read the linked article and I think my brain is having a "you turned intio a CAT!" minute. The gluon-diagram-simplification very short paper linked to in turn from it is also bringing back grad-school days with the 'we see it works, let's find out if there's any chance of understanding why' flavor.

A jewel-like geometric object they call... Time Cube.

Wait, where's my flux-capacitor?

.... so ...magic. Got it.

Edited at 2013-09-20 12:30 pm (UTC)

Doesn't sound like magic.

The basic problem with quantum anything is that it's very hard to think about because our brains expect the world to work in a ways that things just don't, on a quantum scale.

I'd take the article as saying "we've got a candidate general abstraction, an elegant and computationally simple abstraction, for some quantum stuff that used to be really really really hard to calculate. The particular abstraction requires us to formally pitch a couple of axiomatic expectations -- that things affect only the things they're near, and that the probabilities of the possible events always adds up to one -- which makes people uneasy, but we Had Our Suspicions About That from these other results over here."

Even if it is quantum gravity, it's not clear that we'd expect any change in capability whatsoever.

It's basically mathemagics. Or, alternatively, "if we look at this from this so-far-never-viewed mental angle, all the kaleidoscopic puzzle pieces align and fit together at their edges". Worth keeping tabs on just for the Beautifulness component.

--Dave

If nothing else, a jewel-like polyhedron is at least an aesthetic step forward from the XKCD-style Feinmann diagrams.

Munroe Diagrams come with snarky mouseover text.

A -scintillating- jewel-like polyhedron, glowing with lambent coruscations!

--Dave, and we all know coruscation leads to causation

It's the Shining Trapezohedron. Iä Nyarlathotep!

A physicist I know online couldn't vouch for the details (he's a solid state researcher), but he said that while the article is somewhat hyped, this does not appear to be any kind of crank science. Depending on how well the amplituhedron model works when applied to more realistic set of premises, we could be looking at anything from an initially promising failure, to a new and more convenient way of handling complicated calculations in QFT, or even a major conceptual breakthrough that will lead to Nobel prizes and rewriting of physics textbooks.

What raised my hackles is that Wickramasinghe's friends are touting yet another discovery of extraterrestrial life in the Journal of Cosmology and it's suckering all the usual suspects.

I saw people linking to the article and immediately started looking for Wickramasinghe's name...

Panspermia is overwhelmingly probable. There are petakazillions of places in the observable universe for life to originate. The chance that this one here is IT is therefore vanishingly small. Q.E.D.

However, the probability that any evidence for panspermia that is somehow associated with Wickramasinghe is the real deal is also vanishingly small.

You're excluding the case in which life originate independently terakazzillions of times or so, but pretty much never manages to cross interstellar space successfully. Which is, evidence pending, at least as probable as panspermia.

I think he was joking, by implicitly assuming a flat Green's function for propagation.

challenges the notion that space and time are fundamental components of reality.

I've been watching way too much Doctor Who.

They're really pretty wibbly-wobbly, eh?