  We develop a new real-time approach to vacuum decay based on a reduction to a
finite number of degrees of freedom. The dynamics is followed by solving a
generalized Schr\"odinger equation. We first apply this method to a real scalar
field in Minkowski space and compare the decay rate with that obtained by the
instanton approach. The main difference is in the early-time dynamics, where
the decay is faster due to the tail of the wave function. We then apply it to a
cold atom model recently proposed to simulate vacuum decay experimentally. This
approach will be extended to include gravity in a future work.
