CHIRAL RESTORATION IN HOT AND OR DENSE MATTER

Chiral restoration phase transition in hot and/or dense hadronic matte r is discussed in terms of the BR scaling based on chiral symmetry and scale anomaly of QCD, The precise connection between the scalar field that figures in the trace anomaly and the sigma field that figures in the linear a model is established. It is suggested that in hot and/or dense medium, the nonlinear sigma model linearizes with the help of a dilaton to a linear sigma model with medium-renormalized constants. T he relevance of Georgi's vector symmetry and/or Weinberg's ''mended sy mmetry'' in chiral restoration is pointed out. Some striking consequen ces for relativistic heavy-ion collisions and dense matter in compact stars following stellar collapse are discussed.