The Properties Of QCD Vacuum

Studying QCD vacuum properties and non-perturbative QCD is a very important issue for strongly interacting processes.The QCD vacuum condensate and structure of the vacuum are two important aspects of the non-perturbative QCD problems.In fact,the existence and magnitude of the non-perturbative QCD vacuum condensates provide by themselves an important order parameter of the spontaneous chiral symmetry breaking and have many applications in particle and nuclear physics.The existence of QCD vacuum condensates reflects in a direct way the non-perturbative structure of the QCD vacuum.Studying the vacuum condensates of quark, gluon,and their mixture,as well as the structure of non-local quark vacuum condensate,is very important,since it is not only related to the structure of QCD vacuum state,chiral symmetry breaking,which is decisive importance for strong interaction,but also to determination of constituent mass of matter,quark,and hadron masses.They are also related to phase transition from quark-gluon-plasma to hadronic matter in the early universe. At first we give an brief introduction to the strong interaction theory-QCD, and then we study fully dressed quark propagator in the framework of Dyson-Schwinger Equations(DSEs)in the "Rainbow" approximation with three different phenomenological gluon propagators.We select an effective gluon propagators to solve the DSEs at zero temperature and use its solutions to study the structure of non-local quark vacuum condensate and calculate local quark vacuum condensates,quark-gluon mixed vacuum condensates,and quark virtuality in QCD vacuum.At the same time,we also use the solutions of DSEs at zero to study quark masses and Gasser-Leutwyler coefficients of chiral Lagrangian for pseudocasalar Goldstone bosons.Finally,we study Dyson-Schwinger Equations at finite temperature to search for the critical temperature of the transition from a hadronic to a quark-gluon plasma.Our all theoretical results here are in a good agreement with empirical values used widely in literature and many other theoretical calculations.