for each observer in any chosen point of space, false vacuum eventually tunnels into a state with the same potential energy, but which is not a vacuum (it is not at a local minimum of the potential energy—it "can decay"). this state can be seen as a true vacuum, filled with a large number of inflaton particles. however, rate of expansion of the true vacuum does not change at that moment: only its exponential character changes to much slower expansion of the flrw metric. this ensures that expansion rate precisely matches the energy density.