Boltzman Brains are considered to be a problem for for certain cosmological models especially eternal inflation. I have a few questions. Firstly why is this a problem for eternal inflation and not any model fo the universe which leads to a De Sitter space? Surely any model that presumes the future of the universe will exist forever ( as i believe standard LCDM without inflation or eternal inflation does), should have the same problem? Secondly , it seems to me amazingly unlikely that a conscious brain can fluctuate into existence and have thoughts and memories. Of course if there is an infinite amount of time , then no matter how unlikely it will still happen. However, doesnt inflation teach us that a tiny patch of false vacuum can create an entire universe? If so how do we know that the this patch isnt more likely to form than a Boltzman brain? is there any rigorous proof to show that this cant be the case? i.e if we wait long enough how can we say that a brain is more likely than a universe to fluctuate into existence, given that according to inflation all you need for a whole universe is a tiny seed of false vacuum?