Lattice QCD at Non-Zero Chemical Potential and the Resonance Gas Model

We present results from lattice calculations on the thermodynamics of QCD atnon-zero temperature and baryon chemical potential and discuss the role ofresonances for the occurrence of the transition to the quark-gluon plasma inhot and dense matter. Properties of a hadronic resonance gas are compared tolattice results on the equation of state at zero as well as non-zero baryonchemical potential. Furthermore, it is shown that the quark mass dependence ofthe transition temperature can be understood in terms of lines of constantenergy density in a resonance gas.Comment: This paper is based on talks given in July 2003 at the Workshop on Finite Density QCD at Nara, Nara, Japan, and the International Symposium on Color Confinement and Hadrons in Quantum Chromodynamics - Confinement 2003, Wako, Japa