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The Emperor, Darth Vader and the Ultimate Ultimate Theory of Physics

The views expressed are those of the author and are not necessarily those of Scientific American.


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PASADENA—The theory is so obscure there’s not a Wikipedia page about it yet. It might be impossible to formulate mathematically. One theoretical physicist calls it the Emperor Palpatine of theories, even more powerful and inscrutable than the Darth Vader theory that he and others have been studying intensively. And yet it has a purity and elegance that makes them think it captures the deep essence of the natural world. “It’s this sort of ur-theory,” says Nima Arkani-Hamed of the Institute for Advanced Study.

I learned about this strange theoretical brainstorm yesterday while attending a conference at Caltech that has drawn the most intimidatingly brilliant group of people ever assembled in one room. I considered myself lucky when I could understand just the title slide of their presentations. They have come to celebrate the 35th anniversary of the aforementioned Darth Vader theory, known formally as “N=4 supersymmetric Yang-Mills (SYM) theory”. The dark-lord comparison might lead you to believe the theory is irredeemably evil, but in fact theorists consider it their most sublime creation.

The official name requires some unpacking. Supersymmetry is the idea that spacetime, in addition to its usual dimensions of space and time, has an entirely different type of dimension—a quantum dimension, whose coordinates are not ordinary real numbers but a whole new class of number that can be thought of as the square roots of zero. (Yes, that’s allowed. This is quantum physics, after all.) You can’t visualize them, let alone see them, but you can perceive them indirectly: when you rotate an object from an ordinary dimension into a quantum dimension, the object changes what might have seemed to be its essential character. A particle of force becomes a particle of matter, and vice versa. Thus supersymmetry shows that “force” and “matter” are not essential categories, but the same thing viewed differently.

Supersymmetry comes in degrees. The type being sought at the Large Hadron Collider is a minimal version, denoted by N=1, which relates one class of force particle to one class of matter particle. N=4 SYM goes the whole hog: it interrelates all force and matter particles—all, that is, except for those associated with the force of gravity. The term “Yang-Mills” connotes that the theory is a souped-up version of the weak and strong nuclear forces. For gravity, you’d go to N=8.

The high degree of symmetry enormously simplifies the workings of N=4 SYM. The theory does have the disadvantage that it does not and cannot describe the real world, but it is a theoretical physicists’ version of C. elegans, having a purity that makes it a convenient test-bed for conceptual experimentation. Over the past several years, Arkani-Hamed and his colleagues have been trying to reformulate N=4 SYM in a way that makes no reference to space and time, in the hopes it will help them grasp how space and time might emerge from some deeper ingredients.

But now it seems that there is a still greater theory: the Emperor theory, known as (2,0) theory based on the amount and type of supersymmetry it possesses. After his talk, Arkani-Hamed sat down to tell me more about it. It actually goes back to the 1990s and the ferment within string theory back then, although it languished until fairly recently. The unnerving thing about the theory is that physicists think it exists even though they’ve never written it down and are not even sure they can. In this, the Emperor resembles that other creation of the mid-1990s: M-theory, a theory whose existence seems to be implicit in string theory, even though physicists hem and haw when you ask what exactly it is. Both M-theory and the Emperor theory are physics versions of an inchoate feeling you struggle to verbalize.

For something that is as incorporeal as a dead Jedi master, theorists claim to know a lot about the Emperor theory. It resides in five spatial dimensions rather than three. It can be thought of as a collection of the building blocks of M-theory. It is a theory not of strings but of quantum fields, similar in spirit to electrical and magnetic fields. In fact, it provides a true unification of electricity and magnetism, beyond even that envisioned in classical physics: these two phenomena are just different shadows of (2,0) theory projected from five into three spatial dimensions.

Perhaps most intriguingly, (2,0) theory is irreducibly quantum. “It’s the first instance known of a purely quantum-mechanical theory,” Arkani-Hamed says. In fact, the theory reveals a heretofore unsuspected connection between the quantum nature of matter and the structure of spacetime. One may entail the other, bucking the conventional wisdom that they are contradictory, on account of spooky action at a distance.

To judge from how those brilliant people are still at a loss for words, let alone equations, I suspect it will be years before (2,0) theory is the subject of a Scientific American article, let alone a New Yorker cartoon. In the meantime, may all the forces of nature be with them.

George Musser About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. And Then What? 8:09 pm 03/31/2012

    Here’s a thought for you. It is possible to imagine any theory your imagination can dream up and never have to worry about it being proven to be baseless so long as you formulate it such that it is impossible to put it to any scientific test to prove or disprove it. Anyone can do it. It is not restricted to any one IQ level group. If I am told that a particular theory is so obtuse those only a select few can understand it, then I immediately suspect it is baseless. Of course just because I suspect it doesn’t lend any weight to its actual legitimacy or illegitimacy and each of us is free to believe what we will irregardless of whether or no it has any logical demonstrable connection to what we perceive as Reality. If the initial premise or premises of a theory infer a certain number of dimensions with certain characteristics then of course any assumptions that lead to conclusions, which are in agreement with the initial premise or premises, will be saved and those that disagree will be discarded. Also remember that because Mathematics is a Language it may be possible for some who is a gifted Mathematical linguistics to Mathematically describe, using elegant Mathematics, something that is physically impossible to construct just as an artist can depict an imaginary visual scene, or a poet can linguistically describe an imaginary landscape.

    Link to this
  2. 2. gesimsek 8:41 am 04/1/2012

    Where does the matter go when an unstable radioactive element decay?

    Link to this
  3. 3. The Darth Vader Theory | Not Even Wrong 8:47 am 04/1/2012

    [...] of N=4 Super Yang-Mills theory. George Musser of Scientific American is covering the workshop here. He reports that N=4 Super Yang-Mills is being describe as the “Darth Vader theory”, I [...]

    Link to this
  4. 4. Denswei 8:31 am 04/2/2012

    My first thought after reading this was that it was a a-little-too-subtle
    April Fool’s day spoof, no doubt because I read it right after the a-little-too-accurate April Fool’s day parody of Neuroscience.

    Link to this
  5. 5. Postman1 10:17 pm 04/2/2012

    @And Then What? You said:
    “Here’s a thought for you. It is possible to imagine any theory your imagination can dream up and never have to worry about it being proven to be baseless so long as you formulate it such that it is impossible to put it to any scientific test to prove or disprove it. Anyone can do it.”
    Yes, that is unfalsifiable, like Anthropogenic Global Warming theory, and more indicative of a religious belief than science.

    Link to this
  6. 6. hungry doggy 4:51 pm 04/6/2012

    I didn’t understand any of this article. Was it bad writing or is the theory just sheer non-sense?

    Maybe it is time that the highly educated and extremely talented people doing this kind of theoretical research went out and got real jobs. I mean this theory sounds like something my four year old nephew would watch on a Saturday morning cartoon show. Uh, what’s up doc?

    Link to this
  7. 7. hungry doggy 4:56 pm 04/6/2012

    On second thought, was this article an April Fools joke? If it was it wasn’t a funny joke, it wasted my time, and it had the wrong date on it for April Fools Day.

    Link to this
  8. 8. Links for 2012-03-31-Economic Issue | Coffee At Joe's 4:21 pm 04/9/2012

    [...] The Ultimate Ultimate Theory of Physics – Scientific American [...]

    Link to this
  9. 9. Quantum Gravity at Scientific American | Not Even Wrong 2:17 pm 04/17/2012

    [...] some interesting blog entries on these topics. There’s a video here about the Carlip piece, a story about Darth Vader and the Emperor Palpatine that was discussed here, and a recent nice explanation of work on higher spin theories here. This [...]

    Link to this
  10. 10. The (2, 0) Theory: Where does it come from? | 4 gravitons and a grad student 11:25 am 08/23/2013

    [...] (2, 0) theory doesn’t get much press coverage, and when it does, it’s a bit silly. The article I just linked compares it to Star Wars’ Emperor Palpatine, in analogy with what [...]

    Link to this
  11. 11. Hype versus Miscommunication, or the Language of Importance | 4 gravitons and a grad student 1:46 pm 09/13/2013

    [...] (2, 0) theory I put up in the last few weeks, I made some disparaging comments about the tone of this Scientific American blog post. After exchanging a few tweets with the author, I think I have a better idea of what went [...]

    Link to this
  12. 12. Stop the Insantiy, Physics is Cool Enough Without Excessive Hype! 11:16 am 10/1/2013

    [...] or the Language of Importance.” In it, he takes on a recent Scientific American article called “The Emperor, Darth Vader and the Ultimate Ultimate Theory of Physics.”  Yes, ultimate was used twice in the title, that is not a typo.  Matt offers a more congenial [...]

    Link to this
  13. 13. Brad Watson, Miami 10:50 am 03/13/2014

    I’ve discovered unified strings (u21 s19) theory by taking M-theory in its simplest description and adding time analysis to give it symmetry. I’ve collected a great amount of indirect evidence of this and it makes the BIGGEST prediction that all ‘true Earth-like planets’ are built with and run on the algorithm of GOD=7_4 or FOD=6_4…

    M-theory/Supergravity theory
    7D hyperspace + 4 common dimensions = 11D spacetime

    7D hs + 3D regular space + 7 aspects regular time + 4 aspects hypertime = 21D/a st

    -or-

    M-theory/Superstrings Theory
    6D hs + 4D = 10D st

    6D hs + 3D rs + 6a rt + 4a ht = 19D/a st

    See my tweaked NASA conference presentation at http://PlanetNestor.blogspot.com .

    Link to this
  14. 14. Why I Can’t Explain Ghosts: Or, a Review of a Popular Physics Piece | 4 gravitons 1:43 pm 10/31/2014

    [...] is a problem I see pretty frequently. I keep picking on this article, and I apologize for doing so, but it’s got a great example of this when it describes [...]

    Link to this

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