[blueprint]

Conservation of energy is only considered true "locally", but not globally. There are many examples of this in nature, believe it or not. If you wanted to have a system that perfectly conserved energy, how would you expect to measure its existence, or changes in state, anyway?

Besides, even if you assume conservation of particle number, it only has to be eventual conservation. Suppose I borrow some energy from "over here" temporarily and accidentally assemble them into a perfect brain for a second, then they can disperse again, if they like.

A bigger question is, if energy were conserved globally, where exactly did those handy particles come from in the first place anyway?

[raattgift]

Among the de Sitter invariant states for massive fields is the Euclidean or Bunch-Davies vacuum, which allows for pair production with separations greater than the horizon distance. Since our universe seems to be marching towards a state highly similar to the Euclidean vacuum, such pairs seem (a) physically plausible (b) and with some low probability could arise in groups which (c) because they are interacting particles, might nucleate.

Nucleated objects could be long-lasting, which blunts the Boltzmann brain (Bb) picture, as under fluctuation theory the Bb is ephemeral and time-reversible. On the other hand, it's historically been attractive to think of the nucleation of a inflating patch of spacetime (with low enough entropy that structure like galaxies might form as it expands and fragments gravitationally).