 Typically, a quantum Boltzmann brain would suddenly appear from the vacuum (alongside an equivalent amount of virtual antimatter), remain only long enough to have a single coherent thought or observation, and then disappear into the vacuum as suddenly as it appeared.Such a brain is completely self-contained, and can never radiate energy out to infinity.Current evidence suggests that the vacuum permeating the observable Universe is not a Minkowski space, but rather a de Sitter space with a positive cosmological constant.