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15 November 2007, 06:38 PM
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"An Exceptionally Simple Theory of Everything" by Lisi


Garrett Lisi, 39, has a doctorate but no university affiliation and spends most of the year surfing in Hawaii, where he has also been a hiking guide and bridge builder (when he slept in a jungle yurt).

In winter, he heads to the mountains near Lake Tahoe, Nevada, where he snowboards. "Being poor sucks," Lisi says. "It's hard to figure out the secrets of the universe when you're trying to figure out where you and your girlfriend are going to sleep next month."

Despite this unusual career path, his proposal is remarkable because, by the arcane standards of particle physics, it does not require highly complex mathematics.

Even better, it does not require more than one dimension of time and three of space, when some rival theories need ten or even more spatial dimensions and other bizarre concepts. And it may even be possible to test his theory, which predicts a host of new particles, perhaps even using the new Large Hadron Collider atom smasher that will go into action near Geneva next year.

Although the work of 39 year old Garrett Lisi still has a way to go to convince the establishment, let alone match the achievements of Albert Einstein, the two do have one thing in common: Einstein also began his great adventure in theoretical physics while outside the mainstream scientific establishment, working as a patent officer, though failed to achieve the Holy Grail, an overarching explanation to unite all the particles and forces of the cosmos.

Now Lisi, currently in Nevada, has come up with a proposal to do this. Lee Smolin at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, describes Lisi's work as "fabulous". "It is one of the most compelling unification models I've seen in many, many years," he says.

"Although he cultivates a bit of a surfer-guy image its clear he has put enormous effort and time into working the complexities of this structure out over several years," Prof Smolin tells The Telegraph.

"Some incredibly beautiful stuff falls out of Lisi's theory," adds David Ritz Finkelstein at the Georgia Institute of Technology, Atlanta. "This must be more than coincidence and he really is touching on something profound."

The new theory reported today in New Scientist has been laid out in an online paper entitled "An Exceptionally Simple Theory of Everything" by Lisi, who completed his doctorate in theoretical physics in 1999 at the University of California, San Diego.

He has high hopes that his new theory could provide what he says is a "radical new explanation" for the three decade old Standard Model, which weaves together three of the four fundamental forces of nature: the electromagnetic force; the strong force, which binds quarks together in atomic nuclei; and the weak force, which controls radioactive decay.

The reason for the excitement is that Lisi's model also takes account of gravity, a force that has only successfully been included by a rival and highly fashionable idea called string theory, one that proposes particles are made up of minute strings, which is highly complex and elegant but has lacked predictions by which to do experiments to see if it works.

But some are taking a cooler view. Prof Marcus du Sautoy, of Oxford University and author of Finding Moonshine, told the Telegraph: "The proposal in this paper looks a long shot and there seem to be a lot things still to fill in."

And a colleague Eric Weinstein in America added: "Lisi seems like a hell of a guy. I'd love to meet him. But my friend Lee Smolin is betting on a very very long shot."

Lisi's inspiration lies in the most elegant and intricate shape known to mathematics, called E8 - a complex, eight-dimensional mathematical pattern with 248 points first found in 1887, but only fully understood by mathematicians this year after workings, that, if written out in tiny print, would cover an area the size of Manhattan.

E8 encapsulates the symmetries of a geometric object that is 57-dimensional and is itself is 248-dimensional. Lisi says "I think our universe is this beautiful shape."

What makes E8 so exciting is that Nature also seems to have embedded it at the heart of many bits of physics. One interpretation of why we have such a quirky list of fundamental particles is because they all result from different facets of the strange symmetries of E8.

Lisi's breakthrough came when he noticed that some of the equations describing E8's structure matched his own. "My brain exploded with the implications and the beauty of the thing," he tells New Scientist. "I thought: 'Holy ****, that's it!'"

What Lisi had realised was that he could find a way to place the various elementary particles and forces on E8's 248 points. What remained was 20 gaps which he filled with notional particles, for example those that some physicists predict to be associated with gravity.

Physicists have long puzzled over why elementary particles appear to belong to families, but this arises naturally from the geometry of E8, he says. So far, all the interactions predicted by the complex geometrical relationships inside E8 match with observations in the real world. "How cool is that?" he says.

The crucial test of Lisi's work will come only when he has made testable predictions. Lisi is now calculating the masses that the 20 new particles should have, in the hope that they may be spotted when the Large Hadron Collider starts up.

"The theory is very young, and still in development," he told the Telegraph. "Right now, I'd assign a low (but not tiny) likelyhood to this prediction.

"For comparison, I think the chances are higher that LHC will see some of these particles than it is that the LHC will see superparticles, extra dimensions, or micro black holes as predicted by string theory. I hope to get more (and different) predictions, with more confidence, out of this E8 Theory over the next year, before the LHC comes online.


Garrett Lisi's Inspiration - By Bee on Sunday, August 05, 2007
http://backreaction.blogspot.com/200...spiration.html (http://backreaction.blogspot.com/2007/08/garrett-lisis-inspiration.html)

Some weeks ago I asked Garrett Lisi to write a contribution to our Inspiration series. He suggested we instead do an interview by email. I found it a good idea because I thought it might be easier to keep these inspiration posts to a manageable length - after all, I could just stop asking, right?

B: Well, let me start with some introductory questions so readers know what they are dealing with. Ten words that describe Garrett Lisi?

G: "Vell, Zaphod's just this guy, you know?"(I can't follow instructions)

B: Five things that are important in your life?

G: Physics, love, and surfing. I'm only three dimensional -- and no, those aren't in order.

B: Complete these sentences: When I was 15 I thought I could ...
... get a girl to like me by showing off.

- Now I know ...
... all one really needs to do is listen.

- My biggest mistake was/is ...
... not listening.

- I dream of ...
... discovering a beautiful T.o.E. that kicks string theory's ass.

B: Well, next time a girl says ten words, try to listen.

G: Ha!

B: Okay, so among all the possibilities to show off why physics and surfing?

G: Because they're the hardest? No, actually, physics and surfing aren't about showing off. I've always been intrigued by the relationship between mathematics and nature. In school, we learn the math first, then later we learn some physics and see that the math relates to what happens in the world. Then we learn more complicated math -- calculus, group theory, differential geometry, and so on -- and see how this all connects up and describes how the universe works; it's quite wonderful. I got hooked. And the surfing... surfing really nice waves is simply the most fun one can have on this planet.

We have these big brains, and a limited amount of time. So what to do? A lot of people spend their time making money, sometimes with the hope that they'll be able to do what they want after they make it. But you never get that time back. Theoretical physics is the most abstractly beautiful and challenging pursuit there is. It's what I want to spend my time thinking about, so that's what I do.

But all thinking and no action would make for a dull life. So I surf.
A lot.

B: Was that destiny, random choice or your physics teacher and her convincing arguments?

G: Ha, no, my first highschool physics teacher once told my parents: "I'm afraid Garrett just won't ever get anywhere in physics." I remember arguing with him in class constantly -- at one point he stubbornly claimed the force of gravity grew stronger near the center of the earth. He was a chemist.

As a kid I wanted to be an aerospace engineer. And I was very good at math. Turns out I was too good at math -- I got so interested in math and physics classes that I ditched engineering during my second year of college.

B: And what is the beauty that you are dreaming of?

G: Currently, this:



B: Sorry for the delay, E8 got stuck in PI's spam filter... Do you think beauty is in symmetry and simplicity, and should be our guide?

G: I've always found symmetry and complexity to be beautiful. Not complexity in the "random mess" sense, but as a richness of structure... which belies an underlying simplicity. I think nature is a balance of simplicity and complexity in this funny way. Though I do follow one guide for theory building:

"Make everything as simple as possible, but not simpler." - A. Einstein

B: Why then would you want to kick string theory's ass?

G: Because I think it's probably not how nature works.

We have two very good models in fundamental physics, general relativity and the standard model of particles and interactions. A T.o.E. is a theory that combines these two, reproducing them in some limit. (Whether a T.o.E. exists is a separate debate.) It's a hard thing to build, since the structure of these two theories seems very different. GR is fundamentally geometric, while QFT has algebra all over the place. Nevertheless, if you think there is a T.o.E., and you're guided by simplicity, then there should be a unified theory that gives both of these others.

Now, string theory started out with these same motivations, and had a lot of initial success. Back in the eighties people thought the standard model particles were going to naturally come out of the theory at any moment. But they didn't. In order to match the known particles, people have had to build very elaborate structures of branes and orbifolds using all sorts of contrived assumptions and hundreds of parameters. At this point, string theory is a giant kludge, much messier than the structure of the standard model it's supposed to describe. Because of this, I have to think it's probably just not how nature works.

Now, I would never dictate what other physicists should work on. And I even think string theory is still promising enough that it's good for some people to work on it. It's just not for me. What I've been working on recently, as a T.o.E., is a theory that combines all fields of the standard model and gravity in a purely geometric Yang-Mills theory with a single connection.

B: As much as I think your approach towards a ToE is very interesting, I have to say to me that a connection looks neither simple nor beautiful.

Yah, I used to feel that way too -- we see all this messy algebra. But what is a Lie group? It's just a large manifold, with a shape and symmetries described by vector fields -- the Lie algebra elements. A connection and its curvature is a description of how this shape twists around our four dimensional spacetime. And that's all there is to it -- it's purely geometric. This isn't the way physicists usually think of a connection, but mathematicians have been thinking of it this way for at least fifty years, and they've been having a lot of fun.

B: So isn't beauty a very subjective requirement?

G: Yes, it is. But, you know, what makes us physicists and not philosophers is that, at least in principle, our theories need to agree with experiments.

B: You're living on an island, and keep your distance to the academical networks. Do you think that solitude and silence are necessary to our understanding of nature's ways?

G: To a degree, yes. But mostly I spend time in Maui because it's beautiful and the surf is good. And although I work on my own, my wonderful girlfriend is usually around, painting or knitting. And I have friends to hang out with occasionally. Ideally, I think what one needs in life is balance. I like to spend a few hours a day working on physics in silence, and a few hours playing outside or goofing off.

I've been thinking about what the ideal scientific work environment would be, and the best thing I've been able to come up with is a Science Hostel. I envision a large house where theorists could live and work on their stuff alone or in groups while having their meals and living space provided. The idea is to give researchers time, with an easily accessible but undemanding social atmosphere, and as little responsibility as possible. And, of course, it would have to be somewhere beautiful -- with good hiking and other things to do outside. For the past year I've been living near Lake Tahoe -- a great environment for thinking and playing. Anywhere in the mountains would probably be good for a Science Hostel -- even better if it's next to a good ski hill. http://www.timebomb2000.com/forums/smile.gif

The reason I've been out of the scientific network isn't because I thought it was bad, but because I didn't fit in it. I love differential geometry, GR, and QFT, but I don't care for strings. Ten years ago, when I got my Ph.D., the only postdoc positions available in these overlapping areas were in string theory. So, since I had some money saved up, I moved to Maui to work on the puzzle on my own, and learned how to windsurf. Now, ten years later, string theory isn't doing so well and there are starting to be other opportunities in foundational physics. The LQG community has grown significantly -- and they're a wonderful group of people. Also, the FQXi foundation liked what I was doing enough to give me a nice grant. So I felt the time was right to leave my quiet island and start talking with people.

B: Okay, thanks, I think this is sufficient. According to my estimate the attention span of the average blog reader is about 100 words. But most skip the middle section and read the bottomline. So, do you have some last words?

G: Ah, an epitaph...
Do what you love.



16 November 2007, 02:34 PM
Cool article Znanna, thanks for posting that.