When the early universe cools down field configurations may get trapped near a false vacuum. Classically such configurations have infinite lifetime, however quantum corrections allow the system to tunnel through the potential barrier and decay towards the true vacuum. This phenomenon was first described by Coleman in the 90s using path integral techniques with imaginary time. The intuition (in real time) is that a small part of spacetime tunnels trough the potential barrier so that a bubble of true vacuum is formed. This bubble will then rapidly expand which drives the decay in the rest of the universe.
More recently another paper was published where the false vacuum decay was simulated in real time using a classical field theory with initial energy fluctuations big enough to overcome the potential barrier and form classically allowed bubble configurations. The authors found good agreement with Colemans prediction.
In this talk I will review these works and show some (early) results of bubble formation in the full quantum theory. Here we find decay even though the initial energy fluctuations are too small to classically overcome the potential barrier.