Phase transitions in the early and present universe

The evolution of the universe is the ultimate laboratory for studying fundamental physics across energy-scales that span approximately 25 orders of magnitude. The standard models of cosmology and particle physics provide the basic understanding of the early and present universe and predict a series of phase transitions that occurred in succession during the universe's expansion and cooling history. We survey these phase transitions, highlighting the equilibrium and nonequilibrium effects as well as their observational and cosmological consequences. We discuss the current theoretical and experimental programs studying phase transitions in QCD and nuclear matter in accelerators. A critical assessment of similarities and differences between the conditions in the early universe and those in ultrarelativistic heavy ion collisions is presented. Cosmological observations and accelerator experiments are converging toward an unprecedented understanding of the early and present universe.