Instantons and spontaneous color symmetry breaking

The instanton interaction in QCD generates an effective potential for scalar quark-antiquark condensates in the color singlet and octet channels. For three light quark flavors the cubic term in this potential induces an octet condensate and “spontaneous breaking” of color in the vacuum. Realistic masses of the ρand η-mesons are compatible with renormalization-group-improved instanton perturbation theory. It has been argued recently [1, 2] that the physics of confinement in long distance QCD admits an equivalent description in the Higgs picture where color is “spontaneously broken” by an octet quark-antiquark condensate < ψ̄LjbψRai > − 1 3 < ψ̄LkbψRak > δij = 1 √ 6 ξ̄(δiaδjb − 1 3 δijδab) (1) The structure in the color indices i, j, k = 1...3 and flavor indices a, b = 1...3 is such that a physical SU(3) symmetry remains unbroken. The physical vector meson states (gluons) transform as an octet with an equal mass ∼ ξ̄. They have integer electric charge and can be associated with the ρ−, K∗− and ω-mesons. Also the fermions (quarks) transform as a massive octet (plus a heavy singlet) with the appropriate charges to describe the baryon octet (p, n,Λ,Σ,Ξ). (We consider here three flavors of light quarks and neglect the