I would call reheating a vacuum restoration at the end of what could hypothetically be a vacuum collapse know as the inflationary epoch.
Also unless you two and @Snowfire want me to go into the biases and problems with the Laws of Thermodynamics and both the Marbles Problem with the Heisenberg's Principle of Uncertainty and the Katarka Problem in Astronomy in general I don't have anything else to contribute to this topic.
There is no plausible mechanism to undo a vacuum collapse once it's happened. It's a problem of entropy -- the reason collapse is a thing in the first place is that it's energetically favorable to be in a lower vacuum state than a higher vacuum state, but it takes a kick of energy (which could be imparted by quantum tunneling) to make the transition. And because there was a transition to a lower-energy state, the process releases more energy than it consumes, making it possible to trigger a chain reaction. So not only does it take more energy to make the transition the other way, but it releases
less energy than it takes to make a transition, which makes it self-limiting instead of self-perpetuating.
What you might be to referring to as a vacuum "restoration" is probably better described as establishing a new vacuum equilibrium. The ground state is still in the lower energy state -- that is, it hasn't been put back where it was before -- but the resulting condition has settled into a new stable state instead of an unstable transition state. You aren't wrong to suggest that the inflationary epoch was triggered by a vacuum collapse and then eventually reached a new equilibrium state as mass and energy were redistributed. But the reheating epoch isn't well-described by a new equilibrium, because that equilibrium would be
too cold. So
something else must have changed in the universe in order for there to be a widespread increase in energy. And one theory for that "something" is a different vacuum collapse, one that would have released enough energy to push the universe into its more modern state without causing runaway expansion of spacetime.
(It should be noted that "vacuum" is a really bad word for this, as it doesn't carry the right implication in colloquial English usage. It would better be described as "ground state," because there's one for each of the fundamental fields -- that is, there is more than one vacuum, not just the vacuum of space, and all of them exist everywhere. It's called "vacuum" because that ground state defines what we refer to as "empty" space.)
There's really no reason to go into problems with the laws of thermodynamics. We already know -- those are statistical laws, not fundamental laws, and so we should expect there to be biases and anomalies on small scales; they only approximately describe long-term large-scale trends.
For the rest, unfortunately, there's a bit of a language barrier here. In English we don't have any thing called a "marbles problem" with the Uncertainty Principle -- it's possible that we have another name for it, but whatever the Serbian term is doesn't translate to it, so I don't know what problem you mean. And while I
think I understand that Katarka is a Serbian astrophysicist, I'm not having any luck trying to find information in English about what he(?) was studying.
Mary is almost certain that it's whatever is cut off from the rest of reality inside of it that would be the problem. Just not quite sure what it is.
