## A New Theory of Everything? 511

goatherder writes

*"The Telegraph is running a story about a new Unified Theory of Physics. Garrett Lisi has presented a paper called "An Exceptionally Simple Theory of Everything" which unifies the Standard Model with gravity — without using string theory. The trick was to use E8 geometry which you may remember from an earlier Slashdot article. Lisi's theory predicts 20 new particles which he hopes might turn up in the Large Hadron Collider."*
## He's to Physics what Slava Pestov is to PLT. (Score:1, Informative)

## For the non-mathematicians (Score:5, Informative)

A group is a set with an operation (and a couple of extra properties), such as the integers under addition.

The set of a symmetry group is the set of operations that you can perform to an object and have the object remain unchanged. For example, for an equilateral triangle, rotating it by 120 and 240 degrees leaves you with a triangle. So does flipping it around any of its three axes. Add the identity operation, which leaves the triangle untouched and you have the symmetry set for an equilateral triangle. Add an operation and you have a symmetry group.

The U(1) group is the group of all unitary, 1-dimensional operations that leave the inner (dot) product invariant.

The SU(2) group is the group of all unitary, 2-dimensional operations that leave the inner (dot) product invariant and have a determinant of 1.

The SU(3) group is the group of all unitary, 3-dimensional operations that leave the inner (dot) product invariant and have a determinant of 1.

The Standard Model obeys the symmetry found by combining the three above groups: SU(3)xSU(2)xU(1).

E8 is another group with some special properties. The author of the paper is claiming that E8 contains the Standard Model (SU(3)xSU(2)xU(1)), plus the symmetries belonging to gravity.

## Understandable Description (Score:5, Informative)

I found this site easier to understand than the wikipedia link. I warned my trig students about higher dimensions - wait till I tell them about 8-d vectors, they'll love it!

## Re:might be on to something (Score:5, Informative)

## PDF (Score:5, Informative)

here's the abstract for those wondering if they should download it:

Although it is chock full of pretty pictures as well. If he's right, somebody is going to do a story about how the Star of David came to be important (Ezekiel's Wheel?) and want to talk to those soldiers who saw the ship in the woods in Britain that was decorated with a complex pattern with triangles in the middle.

OK, enough mindless rambling...

## Re:GUT from a surfer dude! (Score:5, Informative)

## This is most likely BS. Please see here. (Score:5, Informative)

http://motls.blogspot.com/2007/11/exceptionally-simple-theory-of.html [blogspot.com]

'That's pretty cute!

## Re:Huh? (Score:5, Informative)

It's built upon E8, which is the largest, most complicated (i.e. an exceptional case) finite simple Lie group.

## Re:FTFA (Score:5, Informative)

algebrais 248-dimensional. The universe is still only 3+1-dimensional.## Re:Would've been nicer if you said... (Score:2, Informative)

That would've been far more credible than Einstein... whom, I believe was long dead by the time Norris was conceived.Chuck's an old dude! IMDB says for Chuck Norris: Date of Birth: 10 March 1940, Ryan, Oklahoma, USA

Wikipedia says for Albert Einstein: March 14, 1879 - April 18, 1955

So we've got at latest a 76-year-old Albert Einstein kicking the ass of a 15-year old Chuck Norris. Aw yeah.

## Re:Would've been nicer if you said... (Score:2, Informative)

Albert Einstein: died 18 April, 1955.

Granted, ol' Al would have been 61 years older than Chuck. But geez, is it really that hard to Google something before making an easily-checked claim like, "whom, I believe was long dead by the time Norris was conceived"?

Kids these days.

## Re:I don't understand a thing :( (Score:5, Informative)

Okay, the context is that you've got particles, and they're fundamentally all the same, but they're "turned" in different ways. Think of a ball with 3-color LEDs inside: you can rotate it around three axes, and move it in three directions, and you can also cycle its color and change its blinking pattern. Particles are like that, except that the topology is weird: it's not back to the same orientation until you turn it around 720 degrees, instead of 360 like normal objects. The "gauge group" is the rules for how you can change things. For example, the total color of the universe is white: if you turn something from red to blue, you have to turn something else from blue to red; but you can also create a pair of a green and a purple (anti-green). They write all these rules up in math, and it's tricky because a lot of the features vary continuously (that is, you can rotate something an arbitrarily small amount). And due to the interaction of the rules for one property with the rules for other properties, there are only certain combinations of properties that you can get. They work out all the combinations that you can have and those are what you see as "different" particles that your experiments show. Of course, we don't know what the rules are, and we're trying to figure that out from what combinations of properties we've seen and which ones we're speculating are impossible. And it's hard and takes a lot of calculation to figure out what a candidate set of rules would even mean as far as results. And people are looking at known results and trying to describe them better than "we've done a billion things, and a billion things happened".

Now, the math of rules for how things can interact turns out to be sort of limited; there are basically 4 normal cases, which are boring, and then there are a few exceptional cases, which are interesting. Of these, the hardest to prove stuff about is E8, and it's just now becoming clear what combinations it allows. It's like one of those puzzles where you press a corner and lights change, and you have to turn off all the lights, but it's got dozens of corners and dozens of lights and every time you press a corner a bunch of things change at once, and there are different kinds of corners and it also matters exactly what angle you're holding it at, so there are hundreds of things you can say about each move.

And the mathematicians working on E8 recently said, "well, you can get positions like this and not like that", where "this" and "that" are big complicated lists. And this physicist read that paper and said, "hey, those lists are familiar; I made similar lists of particle interactions". So the proposal is that particles work like E8 in what kind of rules they follow. And it's a really nice theory, because E8 is essentially the most flexible set of rules you can have without it falling apart into just anything being possible (and some rules or properties just not mattering).

## Re:might be on to something (Score:5, Informative)

## Re:This is most likely BS. Please see here. (Score:5, Informative)

Thats what unifying physics is all about. Coming up with one theory to explain everything that used to take multiple, completely unrelated theories to explain

By your analogy, he is showing that apples and oranges are really just different types of fruits.

The best example I can think of is Maxwell's electro-magnetism equations. It might seem obvious today, but it was an amazing breakthrough to realise that electrical fields, currents and magnetism were really just two sides of the same coin. Most lay people of that time must have thought it was a childish misunderstanding to relate lightning and what makes a compass work

I can't speak for whether the theory is flawed or not, but I think you're a little too quick to dismiss it based on high school seniors knowledge.

## Re:This is most likely BS. Please see here. (Score:5, Informative)

So I wouldn't pay attention to Lubos when he says that someone is a crackpot and their ideas aren't feasible. A lot of physicists just look at his comments as free publicity because if Lubos is criticizing it, it usually means that he feels threatened by it, therefore, it could have some promise if it at least got his attention.

## Re:might be on to something (Score:5, Informative)

But note how this theory has made TESTABLE PREDICTIONS - 20 new particles in a specific pattern. That's more than Lubos can claim after years of "research". The theory might be wrong, but at least it's a scientific theory. Lately, in the (rather rarefied) physics community, Lubos really is used as a sort of contrary guide - if Lubos doesn't like it, you might be on the right track.

## Re:This is most likely BS. Please see here. (Score:5, Informative)

Here's what he says about Lee Smolin, author of The Trouble with Physics

No true academic speaks that way about any idea, whether he disagrees with it or not. That's not science, that's fanboi-ism.

## An attempt at a summary (Score:5, Informative)

Different groups have different symmetries. E8 is a group in Lie algebra. The group is "exceptional" and "simple" which is why the article is entitled tongue-in-cheekishly "Exceptionally Simple". The power and beauty of the E8 group has been known for a long time, and it's featured in many theories of physics that have tried to provide an framework for explaining the bewildered world of particles and forces that make up the universe.

What this author has done is use E8 in a new way to come up with a potential new theory that unifies all the forces and fields. This is not *strictly* a theory of everything, as there's a lot more that has to be answered, but if true it provides a geometric model that can give us insight into the underlying principles that are involved, just the way the Periodic Table does for elements.

The guy is no kook, but his theory leaves a lot to be desired. One problem is that E8 and other lie algebras and their associated symmetries have been well-studied for decades, and most all of them have run into intractable problems or incorrect predictions, so this may just be another beautiful theory that doesn't fit reality. Lisi uses a little-known method called "BRST connections" to make it all seem to work, which most physicists are unfammiliar with. Another is that his theory actually forces something physicists call as "spontaneous symmetry breaking" into the calculations to make it fit what we know to be true in the "standard model". Many people feel this is putting the cart before the horse; they would prefer a theory where the symmetry is broken in a "nautral" way and the "standard model" of the universe just naturally falls out of it. Lisi's theory doesn't really tell us WHY this is the case, it just says it is, but here's the symmetry that underlies it and which you apply it to.

Another problem is that the theory is still new and doesn't have an quantitative predictions as of yet... there's a lot of math that needs to be done, and it's not clear that such calculation *can* be done given the contraints of his theory. At issue is something known as the "Coleman-Mandula" theorem, which basically says a lot of what Lisi does in his theory doesn't work if there are subgroups in the algenbra that are equivalent to what are known as Poincare groups. Lisi says this doesn't apply to his new theory because it posits that the vacuum of spacetime doesn't have Poincare symmetry but instead is deSitter space. Well, the idea of deSitter space is well-known and has been examined in theoretical physics for decades as well, but there are a lot of problems with it. One is that the "Smatrix", which physicists love so much in making calculations in theories with Poincare symmetries, no longer works and simply becomes an approximation.

The theory also predicts a very LARGE cosmological constant, which is contrary to observation, but there are other theories that explain how this is not actually a problem, so that might not be an issue. Perhaps the largest obstacle of the theory, once the calculations can be figured out, is that it pretty much obsoletes all of String Theory in favor of something like Loop Quantum Gravity. This will make a LOT of string physicists very unhappy.

Lisi's theory will probably not be the last work in physics, but it might bring us a step closer to a real "Theory of Everything". The truth is physicists have been toying with similar geometric approaches and arrange particles in tables and trying to tie in gravity for decades now and every new theory looks great but never quite actually works out. The fact that the universe can *almost* be described via these methods probably tells us we're on the right track, but a true

## Re:This is most likely BS. Please see here. (Score:1, Informative)

If anyone is interested in Garrett's reply to Motl's ad hominems, here it is: http://www.physicsforums.com/showpost.php?p=1496330&postcount=14 [physicsforums.com]

This is actually a relatively interesting approach, but I'm skeptical about the predictions of 20 new particles Garrett's theory makes. Ultimately it's up to experiment, as opposed to (say) a string of insults a maundering Harvard professor makes, that determines whether or not this theory is false or not.

## Re:FTFA (Score:5, Informative)

He's not saying space has 248 dimensions, he's describing the geometry of a polygon. If you read the paper, he's only invoking 3 spatial dimensions and one time dimension to define our universe.

Let's say you've got a cube, and each corner of the cube represents the properties of a subatomic particle. You can have a total of 8 subatomic particles and you can create a direct line between any point on the cube and any other.

E8 is a 248-dimensional set of lines connecting the points of a 57-dimensional imaginary object. What he has done is merge the E8 "object" with the various subatomic particles and used the remaining unassigned points to predict the features of those particles we have yet to detect. In essence, he's created a math representation of a periodic table of subatomic particles.

People with Ph.D's in mathematics aren't expected to understand the theory. People with Ph.D's in particle physics aren't expected to understand the theory.

Quite frankly, there's a serious audience of around one hundred people on the planet that can actually grasp what he's saying, and they seem to be divided about it and its ramifications.

~ J. Barrett

## Re:GUT from a surfer dude! (Score:3, Informative)

## Think properties, not dimensions. (Score:5, Informative)

Now, there are other valid combinations of properties within E8 beyond the ones that represent the particles in the standard model, and these combinations would represent new particles that we have not seen before, if the model is correct.

## Re:Wikipedia link to E8 - Still makes nooooo sense (Score:5, Informative)

Holy crap! - I can read all the words, but none of it makes any sense. It's like the took regular English words and gave them all different meanings. I haven't felt this uncomprehending in a loooong time - and even the dumbness felt from quantum chemistry pales to this.

http://en.wikipedia.org/wiki/Group_theory [wikipedia.org]

Which then gets you here:

http://en.wikipedia.org/wiki/Symmetry_group [wikipedia.org]

Once you get those two, you can hit:

http://en.wikipedia.org/wiki/Differentiable_manifold [wikipedia.org]

and you're very close to a general understanding of the shape (no pun intended) of what E8 is all about, and can dive into:

http://en.wikipedia.org/wiki/Lie_group [wikipedia.org]

## Re:Wikipedia link to E8 - Still makes nooooo sense (Score:3, Informative)

## Re:PDF (Score:3, Informative)

http://www.physicsforums.com/showthread.php?t=179527 [physicsforums.com]

http://backreaction.blogspot.com/2007/08/garrett-lisis-inspiration.html [blogspot.com]

## Re:GUT from a surfer dude! (Score:2, Informative)

## Re:Wikipedia link to E8 - Still makes nooooo sense (Score:4, Informative)

http://uk.youtube.com/watch?v=-xHw9zcCvRQ [youtube.com]

## Re:GUT from a surfer dude! (Score:4, Informative)

That said, the reason I believe entheogens can foment scientific breakthroughs as discussed is attributable to two factors brought about by the process.

1) The manner in which these serotonin receptor 'confusers' suppress (or amplify, again LSD) our everyday neuroses. The immediate and lingering effects of 'clear headedness' allows for purer thought. Often, when the person taking entheogens is a mush-melon who goes in to the experience trivially to 'get off' their 'pure thought' afterglow leads to far fetched conclusions. Take the same molecule and apply it to molecular biologist or highly trained Buddhist and truly remarkable work can be accomplised.

2) On an individual level, entheogens can be described as agents for allowing the subject a unique perspective temporarily removed from their primary and secondary socializations (as described in sociology), that is to say the scripts that define your personality are removed to a certain degree. This is often described as 'ego death.' This is also a primary goal of Buddhist and Taoist meditative ritual. Even a little taste of 'ego death' can inspire mountains of unencumbered thought.

This can manifest itself in realizations such as "Jesus why am I so weak about smoking cigarettes? Where does that come from? It's so clear now how to turn it off" or "There's absolutely no reason why a DNA template subset can't be exponentially amplified using heat-stable DNA polymerases."

## Re:I don't understand a thing :( (Score:3, Informative)