COLOR GAUGE GROUP AND NEW LOW-ENERGY PHENOMENA

The unbroken color gauge group SU(3)c may arise as a consequence of the spontaneous symmetry breaking of some larger group. The possible uniqueness of the color gauge group is examined under a set of minimal assumptions. Under these assumptions it is shown that the color groups Gc=SU(4), SU(5) (and perhaps E6) are essentially uniquely singled out as possible alternatives of the standard SU(3)c assignment. The symmetry breaking to SU(3)c can take place without the introduction of a gauge hierarchy. The consequences of Gc=SU(5) are discussed, including new phenomena which occur between 100 GeV and 1 TeV, and agreement with the standard model at energies below 100 GeV. © 1990 The American Physical Society.