Cosmological phase transition

The success of the Big Bang model led researchers to conjecture possible cosmological phase transitions taking place in the very early universe, at a time when it was much hotter and denser than today.

[1][2] Any cosmological phase transition may have left signals which are observable today, even if it took place in the first moments after the Big Bang, when the universe was opaque to light.

[3] The Standard model of particle physics, parameterized by values measured in laboratories, can be used to predict the nature of cosmic phase transitions.

A system like an iron bar being cooled below its Curie temperature can have two states at the same lower energy with electron magnetic moments aligned in opposite directions.

[15] In the early universe the chemical potential of baryons is assumed to be near zero and the transition near 170MeV converts a quark-gluon plasma to a hadron gas.

[14]: 305 Lattice studies of the electroweak model have found the transition to be a smooth crossover, taking place at 159.5 ± 1.5 GeV.

[19] The conclusion that the transition is a crossover assumes the minimal scenario, and is modified by the presence of additional fields or particles.

Particle physics models which account for dark matter or which lead to successful baryogenesis may predict a strongly first-order electroweak phase transition.

[14]: 305  Cosmological phase transitions may also have taken place in a dark or hidden sector, amongst particles and fields that are only very weakly coupled to visible matter.

[21] Among the ways that cosmological phase transitions can have measurable consequences are the production of primordial gravitational waves and the prediction of the baryon asymmetry.