Editing Inflaton (section)

=== Phase transition to true vacuum ===
{{Unreferenced section|date=August 2019}}
Inflationary theory further postulates that this "inflationary vacuum" state is not the state with globally lowest energy; rather, it is a "[[false vacuum]]", also known as a ''[[metastable]]'' state.

For each observer at any chosen point of space, the 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, the 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.