Friday, November 16, 2007

An Exceptionally Simple Theory of Everything

Garrett Lisi, an unemployed physicist (much has been made of his being a surfer, as though that matters), has made some serious waves in the physics world by publishing his "An Exceptionally Simple Theory of Everything."

Lisi's theory manages to unite the four fundamental forces of nature: the electromagnetic force; the strong force, which binds quarks together in atomic nuclei; the weak force, which controls radioactive decay; and gravity (which has been the problem with the Standard Model).

The real beauty of Lisi's model is that is provides testable hypotheses.

From The Telegraph UK:

[H]is 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.

And:

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.


And:

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 crap, 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.


Very cool. It will be exciting to watch this and see how it turns out. It's such an elegant and simple theory when compared to string theory.


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