This is incredibly interesting, and I can't really wrap my head around it. In a way, such "Boltzmann Brains" would be similar to "Tralfamadorians" from Kurt Vonnegut's Slaughterhouse 5. This would be with regards to their lack of an "arrow of time". Everything would be, and everything would not be. As to the actual formation of such a thing, that's where I'm completely lost. The other issue I'm having is what exactly a post black hole universe would be like?
Hey I'm with you. This idea is really challenging. As I said though, incredulity is not reason enough to not consider it. If the physical laws allow for such an entity, it should come into existence given enough time. I suppose it stems from the idea that a random process (i.e., not selection within a system over time) can produce complexity - albeit mind-bogglingly infrequently. And apparently - if the the current effects of Dark Energy persist indefinitely into the future, the universe will eventually just be black holes. Once those black holes disintegrate all that will remain will be photons, neutrinos, electrons, and positrons flying around randomly and almost never encountering each other. This is apparently the "Dark Era". And no one really knows what we should expect to occur post Dark Era.
The second law of thermodynamics is one of my favorite from any area of science. The entropy of a system shall not decrease except in certain cases where the entropy of another system is increased. This increase over a long enough period of time results in those mind-boggling creations and weird combinations. I guess then, if there is a such thing as a multiverse, are they all experiencing these increases in entropy? Could there be a nearby universe that is not experiencing an increase, thus helping to result in our increase? The more you think about it the more complex this gets. Okay, that does make sense, as sad as it is. I still barely have any understanding of how black holes work, especially what happens to the matter inside of them. If they disintegrate, are they then slowly releasing the base atoms that were absorbed into it? The concept of a Dark Era is terrifying.