First-Order Phase Transition
The Big Bang model describes the universe originating from an extremely hot, dense state undergoing a first-order phase transition, analogous to water freezing.
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The statement of the theorem
For a first-order phase transition involving a scalar field , the dynamics are governed by the potential energy density . The transition occurs when the free energy functional develops multiple minima. The transition rate is determined by the barrier height and the vacuum expectation value . The transition proceeds via bubble nucleation, characterized by the action : \nwhere , and is the bubble wall tension.