1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Why SU(3)xSU(2)xU(1)?

  1. Jan 2, 2017 #41
    "Alas, the group SU(3) is not the unit octonions. The unit octonions do not form a group since they aren't associative. SU(3) is related to the octonions more indirectly. The group of symmetries (or technically, "automorphisms") of the octonions is the exceptional group G2, which contains SU(3). To get SU(3), we can take the subgroup of G2 that preserves a given unit imaginary octonion... say e1. This is how Dixon relates SU(3) to the octonions. However, why should one unit imaginary octonion be different from the rest? Some sort of "symmetry breaking", presumably? It seems a bit ad hoc."
    The complexified octonions (which I label S = C⊗O) is not a division algebra. Its identity can be resolved into a pair of orthogonal idempotents, and it is from this resolution of the identity that much of what's interesting and beautiful about S arises. This resolution requires a direction in imaginary O space be chosen, and the subgroup of G2 leaving this direction invariant is SU(3). With respect to this resolution S splits into 4 SU(3) multiplets: singlet; antisinglet; triplet; antitriplet. This notion was used by Gürsey at Yale in the 1970s. There's nothing ad hoc about it. It's an ineluctable and beautiful part of the maths. There's nothing vague about it, as two books and numerous papers have attempted to demonstrate ad nauseam. Sigh.
  2. Jan 3, 2017 #42


    User Avatar
    Gold Member

    I wonder if this is related to the branched covering of S4 by CP2. (see atiyah an also google https://www.google.es/search?sourceid=chrome-psyapi2&ion=1&espv=2&ie=UTF-8&client=ubuntu&q=S4 branched covering CP2&oq=S4 branched covering CP2&aqs=chrome..69i57.5235j0j7 ). CP2 fibered with S3 should have an isometry group very as the standard model group.
  3. Jan 3, 2017 #43
    Well, if you have a house, and inside that house there is a very nice and perfectly functional WC, why go outside and dig a hole in the ground to serve the same purpose, but not as well?

    I haven't figured out how to include a quote from a previous comment, but this is in reply to arivero's comment above.
  4. Jan 4, 2017 #44
    gdixon, what do you do for dynamics?
  5. Jan 4, 2017 #45
    Dynamics, hmm. A possibly poor metaphor: it's like asking Mendeleev, after he presents you with the periodic table, where's the chemistry? A perfectly valid question, and Mendeleev certainly would have been able to answer that. My attitude has always been this:

    Adding O to P=C⊗H, yielding T=C⊗H⊗O, results ultimately in an expansion of the Dirac algebra and its associated spinor space, which is where the particle fields reside. As I understand it, one starts building dynamics into Dirac maths by building a Lagrangian density. All the pieces needed to do that are present in T-maths, they're just bigger. So, if one wishes one can construct a Lagrangian density for this more complicated spinor space, and its associated 1,9-spacetime Clifford algebra (the expanded Dirac algebra). I did this in my first book 22 years ago, guaging the result. Very nicely one can read from this all viable particle interactions, for it is not hard to pick out from T^2 the bits that represent individual quarks, leptons, anti-quarks, and anti-leptons.

    And then there is the matter of the quarks themselves, and the extra 6 space dimensions, neither of which are seeable in any conventional sense, and both of which are associated with the 6 octonions units that do not occur in the resolution of the identity. As I showed in my last published paper, taking this unseeableness to its logical mathematical conclusion implies that from our 1,3-spacetime we can also not see the anti-matter part of the full 1,9-spacetime, so we appear to live in a universe dominantly matter.

    Anyway, I'm retired now. I'll present my last paper at a conference this summer, then i'm dropping the mike.
  6. Jan 4, 2017 #46
    Keep in mind: what I did was a proof of concept. My hope is that reality is more subtle than this.
  7. Jan 5, 2017 #47

    One idea to keep in mind is phase transitions. For example, water in a steam state or liquid state is much more symmetric than an ice state with flaws and cracks. If you rotate the ice with streaks and cracks, it's easy to see you lost rotational symmetry.

    Similarly, imagine spacetime itself, as we perceive it now, in an "ice-like" state, with temperatures far cooler than the big bang. The big bang temperature would be akin to "boiling" temperature for spacetime. And this is why one studies quantum gravity, in hopes of finding a deeper theory that can describe the extreme phase transitions expected to occur at black hole event horizons and the big bang itself. Essentially, anywhere one would expect singularities in Einstein's general relativity (akin to an effective spacetime hydrodynamics), this would be the realm of quantum gravity and unified field theory.

    Hence, from the perspective of phase transitions, SU(3)xSU(2)xU(1) would be the result of a broken higher symmetry, due to the Universe entering an "ice-like" state after 13.82 billion years. This is reasonable, as my living room is nothing like a black hole event horizon.

    The whole point of building huge particle accelerators is to reproduce extreme energies, forcing a phase transition to a more symmetric state for a brief time, and take a snap shot of the resulting symmetry breaking that occurs after a high energy collision.

    The appeal of E8, for example, is that it is a unique Lie algebra (mathematically) which gives elegant rules for scattering a robust set of particles (bosonic & fermionic), in a closed manner, where the observed inelegant symmetries of the standard model can be seen as part of a larger symmetric whole.

    The quest continues...
  8. Jan 5, 2017 #48
  9. Jan 6, 2017 #49

    "Keep in mind: what I did was a proof of concept. My hope is that reality is more subtle than this."

    By this I do not intend to cast doubt on the necessity of C⊗H⊗O as a basis
    for any viable TOE. I have no doubt. None. The algebra is necessary
    because parallelizable spheres are necessary. And once you have it,
    the mathematics gives you everything else.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Why SU(3)xSU(2)xU(1)?
  1. Why 3+1 dimensions? (Replies: 29)

  2. Why SU(2) spin networks? (Replies: 19)

  3. Why SU(3)xU(1)? (Replies: 3)