I'm trying to understand more about how our present universe is supposed to be the result of a false vacuum falling to the present vacuum energy. I've been told (correct this if it's wrong), the universe initially underwent a kind of hyperinflation, expanding exponentially due to a much higher vacuum energy than now. But at some point this high vacuum energy somehow fell to a lower vacuum energy which resulted in a much slower expansion rate. Is this much true, and can someone please supply a few more words about this? For example, was it the inflaton field that decayed into the present particles as the vacuum energy fell? Is this the point where the higgs mechanism gave particles mass? What is meant by vacuum energy? Is this the same concept that the fields had a zero-point-energy. Did the fields of nature during inflation still obey the Heisenberg Uncertainty Principle such that the energy of the field(s) times the duration they existed could be larger than today? Thanks.