Constraints onNcin extensions of the standard model

Robert Shrock
2007 Physical Review D  
We consider a class of theories involving an extension of the Standard Model gauge group to an a priori arbitrary number of colors, N_c, and derive constraints on N_c. One motivation for this is the string theory landscape. For two natural classes of embeddings of this N_c-extended Standard Model in a supersymmetric grand unified theory, we show that requiring unbroken electromagnetic gauge invariance, asymptotic freedom of color, and three generations of quarks and leptons forces one to choose
more » ... orces one to choose N_c=3. Similarly, we show that for a theory combining the N_c-extended Standard Model with a one-family SU(2)_TC technicolor theory, only the value N_c=3 is allowed.
doi:10.1103/physrevd.76.055010 fatcat:jikjehgp7vbsjmblkscyxxjej4