Chiral effective theory of strong interactions

Abstract

The review of chiral effective theory (CET) is given. CET is based on quantum chromodynamics and describes the processes of strong interaction at low energies. It is proved, that CET comes as a consequence of the spontaneous violation of chiral symmetry in QCD - the appearance of chiral symmetry violating vacuum condensates. The Goldstone theorem for the case of QCD is proved and the existence of the octet of massless Goldstone bosons (pi, K, eta) is demonstrated in the limit of massless u,d,s quarks (or the triplet of massless pions in the limit m_u,m_d->0). It is shown, that the same phenomenon - the appearance of quark condensate in QCD - which causes the Goldstone bosons, results in appearance of violating chiral symmetry massive baryons. The general form of CET Lagrangian is derived. Few examples of higher order corrections to tree diagrams in CET are given. The Wess-Zumino term (of order p^4 term in CET Lagrangian) is presented. Low energy sum rules are presented. QCD and CET at finite temperature are discussed. In the framework of CET the T^2 correction to quark condensate in QCD at finite temperature T is calculated and the results of higher order temperature corrections are demonstrated. These results indicate on phase transition in QCD at T \sim 150-200 MeV. The mixing of current correlators in order T^2 is proved.