QCD Instanton Vacuum Research Articles

Instanton vacuum at non-zero temperatures

Using the variational principle developed previously for the QCD instanton vacuum at zero temperature, we investigate the ensemble of instantons and antiinstantons at all temperatures. We find a rapid decrease of the pseudoparticle density at T∼(1−2)Λ MS for SU 2 and, especially, for SU 3 gauge groups. This phenomenon may serve as a mechanism for the restortion of chiral symmetry at high temperatures ( T⋍Λ MS ).

Chiral condensate in the instanton vacuum

We suggest a new mechanism for spontaneous violation of chiral symmetry in the instanton vacuum of QCD. It is due to the smearing of the would-be zero fermion eigenmodes of individual pseudo-particles in the instanton medium. Using the characteristics of the medium previously found we calculate the value of the quark condensate 〈 ΨΨ 〉 and the effective quark mass m ∗ in a good agreement with the phenomenology.