Thinking about a major puzzle in the NCG approach to the standard model, I remember that sci.physics.research, via Baez’ weeks, was very fond of triality (in the way of Evans?) to justify why some dimensions allow supersymmetry. And this pivots over SO(8), for which I asked a couple of abusive questions in mathoverflow:
Does ??(32)???8×?8 relate to some group theoretical fact?
Why SU(3) is not equal to SO(5)?
The second one included a nice ascii sequence of dynkin diagrams, using
o====o  SO(5), isometries of the sphere S4
o----o  SU(3) are the isometries of CP2
o    o  SU(2)xSU(2), isometries of  S2xS2. Also SO(4), so isometries of S3
I compared
        o                  o                         o
       /                                        
      /                                          
o----o    SO(8)    o----o     SU(3)xSO(4)    o====o     SO(5)xSO(4)
      \
       \
        o                  o                         o    
and I wonder if I should add Pati-Salam
             o             
                                             
                                               
o----o----o     SU(4)xSU(2)xSU(2)     
     
      
             o                
  
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