Dynamical Model Of QCD Vacuum And Quark Confinement

It is well known that symmetry breaking and quark confinement are two open problems in theoretical physics. Both of these important problems are closely related to the dynamics of physical vacuum. The aim of this dissertation is to try to study these problems and report some heuristic arguments. The thesis consists of four chapters. In chapter 1 and 2, the concepts of symmetry breaking and physical vacuum are introduced. In terms of the mechanism of dynamical symmetry breaking including theory of effective potential, Nambu Jona-Lasinio (NJL) mechanism and Schwinger mechanism, the dynamical symmetry breaking of supersymmetry Higgs model and supergauge model are investigated. In chapter 3, the QCD and non-topological soliton model are presented. And in chapter 4, the physical vacuum has been introduced into a simple QCD model, by using the NJL mechanism, the dynamical symmetry breaking of this QCD model has been discussed and it is pointed out that the physical vacuum of QCD is a bound state of quark-antiquark pairs which can be viewed, generally, as a nearly perfect color dia-electric medium. To the lowest-order approximation in h, an important relation between the vacuum expectation value of color gauge fields and scalar fields is also derived by solving the Euler equation for the gauge fields. Based on this relation the color gauge potential is given which can be used to explain the asymptotic behavior and confinement of quarks in a hadron. The confinement behavior at finite temperatures is also investigated and shown that color confinement at zero temperature can be melted away at high temperature.