Some of Fields medalist Alain Connes‘ revolutionary ideas shed light on how to understand the ‘zoo’ of elementary particles thrown up by accelerators like the LHC. If Connes is right, the key to the fundamental nature of matter lies in graffiti carved on a bridge in Dublin in 1843.
The graffiti was carved by this man William Rowan Hamilton on Brougham bridge as the ebullient mathematician was passing on a walk with his wife. According to a plaque there, it read:
i^2=j^2=k^2=ijk=-1
I am in Dublin later this week and will be taking my camera.
So how does this answer the mysteries of the Universe? According to Alain Connes in his chapter of the multiauthored volume On Space and Time, spacetime indeed has ‘extra dimensions’ but these extra dimensions are not those of any usual kind geometry (curled up or whatever as in string theory) but something far more imaginative; they are given by a symbolic algebra defined by two copies of this graffiti.
Connes is a Fields medalist, which is like a Nobel Prize for mathematicians (who were left out in the will of Alfred Nobel. Incidentally, there is no merit to the popular myth that this was because of an affair between his wife and a mathematician; he never married). So what that means is that the actual mathematics behind his theory is very deep and very advanced; I’ll only be touching on the easier parts in this post.
Well, lets get the maths over with. The main idea we need is that geometry is algebra.
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Comments
Supercomplex algebra
October 16, 2008 by Anonymous, 1 year 5 weeks ago
Comment id: 32416
Does this equation define a kind of supercomplex algebra? Are you suggesting that no mathematicians until now has think about a supercomplex algebra since 1843? I cannot believe it.
Re: Supercomplex algebra
October 22, 2008 by Halliday, 1 year 4 weeks ago
Comment id: 32419
This "Supercomplex algebra" is called the Quaternion algebra. They are found in the algebra of three dimensional rotations (so they are, in a sense, at least, found in Quantum Mechanics in all cases involving spin [spin(3), so(3), and su(2)]). This is one of the simplest non-commutative algebras.
In fact, there are computer graphics systems that use quaternions.
The Standard Model uses an even larger algebra (u(1) + su(2) + su(3), where '+' is being used in place of the kronecker sum).
It sounds like Alain Connes has an approach using a fiber bundle space (which extends the tangent spaces of General Relativity) having a structure of a product of two Quaternion spaces (sort of like q + q, where 'q' is the appropriate Quaternion algebra). (Actually, since the new space extends the tangent space of the spacetime manifold, I suppose it would be something like q + q + R4.)
(One can go even farther, as a "Supercomplex algebra", to the Octonion algebra, which also looses associativity, in addition to commutativity. This is intimately related to the exceptional Lie algebras, which some consider to be the most beautiful mathematical structures known. In a sense, it would be a "shame" if the Universe were to settle for any lesser algebra than the largest [finite] exceptional Lie algebra: E8.)
I would be very interested in what "good part of the zoo of particles found in particle accelerators" "exactly match" in this approach taken by Connes and his collaborators.
I kind of like at least some of the ideas of "noncommutative geometry". However, I certainly wouldn't start using the term "quantum geometry" until I got to the point of endorsing it as "the" basis upon which the Theory of Everything (ToE) "should" or "will" be built.
Just some of my thoughts on this matter.
David
Reply to David
November 21, 2008 by Anonymous, 1 year 1 day ago
Comment id: 33003
Dear David,
came across your post.I s a bit like a fiber bundle but the `fiber' is not a usual space as its coordinates are non-commutative, the quaternion algebra. You could say algebra bundle. But the new bit is that Connes shows that the Geometry in the nc fiber direction, i.e. the Dirac operator, encodes the
two dozen undetermined constants in the standard model and imposes constraints between some of them (mass relations). You can see his chapter of `On Space and Time' where he explains why this is fundamentally different from usual fibre bundles. The treatment if SU_3 is a bit by hand and might be improved one day. Whats mainly missing is no explanation of why there are duplicated families of particles in this theory any more than in the standard model. But for each family its a good fit with explanatory power. I agree would be cool to try octonions instead of quaternions. You'd need nonassociative geometry and I may talk about that in a later post.
Shahn Majid
Thank you for posting this here.
October 15, 2008 by Anonymous, 1 year 5 weeks ago
Comment id: 32409
I enjoyed reading it.