Bubble growth and droplet decay in the quark-hadron phase transition in the early Universe

When the Universe was about 10 μsec old, it underwent a phase transition in which the quarks and gluons condensed into hadrons. We assume that this phase transition was of first order and study how the Universe evolved through the mixed phase in a scenario with small initial supercooling and monotonically growing hadronic bubbles. Nucleation of bubbles, collisions of shock fronts preceding the bubbles, arrestation of bubble growth by the reheating due to these collisions, subsequent slow growth of the bubbles to fill the entire Universe, condensation of baryon number, death of the remaining quark matter droplets, and the resulting density perturbations are discussed. A (1+1)-dimensional approximation is frequently used to make analytic calculations possible.