ON THE QCD PHASE-TRANSITION AT FINITE BARYON DENSITY

We investigate the QCD chiral phase transition at finite chemical pote ntial mu, using the renormalization group (RG) to characterize the inf rared behavior of sigma models constrained by the flavor and spacetime symmetries. The results are similar to those obtained from RG analysi s of the finite temperature transition at zero baryon density. When th ere are more than two massless flavors of quarks, a first order transi tion is predicted for the entire phase boundary. In the two flavor cas e, a boundary with first and second order regions separated by a tricr itical point seems most likely. We discuss the real-world case with tw o light quarks and an intermediate mass strange quark. Improved lattic e data on the temperature transition will strongly constrain the possi bilities for the phase boundary. (C) 1998 Published by Elsevier Scienc e E.V. All rights reserved.