Inhomogeneous nucleation in a quark-hadron phase transition - art. no. 054904

The effect of subcritical hadron bubbles on a first-order quark-hadron phas e transition is studied. These subcritical hadron bubbles are created due t o thermal fluctuations, and can introduce a finite amount of phase mixing ( quark phase mixed with hadron phase) even at and above the critical tempera ture. For reasonable choices of surface tension and correlation length, as obtained from the lattice QCD calculations, we show that the amount of phas e mixing at the critical temperature remains below the percolation threshol d. Thus, as the system cools below the critical temperature, the transition proceeds through the nucleation of critical-size hadron bubbles from a met astable quark-gluon phase (QGP), within an inhomogeneous background populat ed by an equilibrium distribution of subcritical hadron bubbles. The inhomo geneity of the medium results in a substantial reduction of the nucleation barrier for critical bubbles. Using the corrected nucleation barrier, we es timate the amount of supercooling for different parameters controlling the phase transition, and briefly discuss its implications to cosmology and hea vy-ion collisions.