CHIRAL SYMMETRY RESTORATION AS THE GEORGI VECTOR LIMIT

Abstract

I discuss recent work done with Gerry Brown on chiral phase transition at high temperature and/or density described in terms of Georgi's vector limit. The notion of ``mended symmetry" is suggested to play an important role in understanding the properties of hadrons in dense and/or hot matter before reaching the phase transition. It is shown that while the QCD vacuum in baryon-free space is resistant to ``melting" up to the critical temperature, baryon-rich medium can induce the vacuum to become softer in temperature: the hadron masses drop faster in temperature when baryon matter is present.