Isentropic equation of state of 2-flavor QCD

Using Taylor expansions of the pressure obtained previously in studies of 2-flavor QCD at nonzero chemical potential we calculate expansion coefficients for the energy and entropy densities up to O(mu(6)(q)) in the quark chemical potential. We use these series in mu(q)/T to determine lines of constant entropy per baryon number (S/N-B) that characterize the expansion of dense matter created in heavy ion collisions. In the high temperature regime these lines are found to be well approximated by lines of constant mu(q)/T. In the low temperature phase, however, the quark chemical potential is found to increase with decreasing temperature. This is in accordance with resonance gas model calculations. Along the lines of constant S/N-B we calculate the energy density and pressure. Within the accuracy of our present analysis we find that the ratio p/epsilon for T > T-0 as well as the softest point of the equation of state, (p/epsilon)(min)similar or equal to 0.075, show no significant dependence on S/N-B.