Bubble free energy at the quark-hadron phase transition

We calculate the free energy of finite droplets of quark-gluon plasma, and of finite hadronic bubbles in the bulk plasma, near the confinement phase transition. We sum over free quark and gluon energy levels in the presence of MIT bag boundary conditions. We find that the curvature term in the free energy, proportional to the radius of the droplet or bubble, is far more important than the contribution of the surface tension, proportional to the radius squared. This affects the critical radius for nucleation of plasma droplets in the superheated hadron gas, and seems to lead to instability of the plasma (even when not supercooled) against nucleation of hadron gas bubbles.