Confinement and the consistency of Yang-Mills theory

It is shown that if the Yang-Mills equations, including the generalized form of Gauss's law, are required to hold when acting on physical states, then as a result of the Wigner-Eckart theorem those states must be color singlets. Consequently the generators of the gauge group cannot be physical observables. It is also argued that the potential energy of the constituents of a color-singlet state probably becomes infinite at large separation, so that Yang-Mills theories necessarily exhibit confinement. In particular, a Coulomb-type behavior of the gauge fields is excluded