Quark confinement and the puzzle of the ninth axial-vector current

Abstract

A solution to the U(3) × U(3) problem—the absence of a ninth pseudoscalar Goldstone boson—is proposed. The mechanism for eliminating the unwanted Goldstone boson involves the same infrared instabilities of Yang-Mills theory which confine quarks and eliminate physical "color" states. A formal argument is presented, and two models of quark confinement illustrate the mechanism involved in eliminating the spurious massless state.