The possible resolution of Boltzmann brains problem in phantom cosmology

Abstract

We consider the well-known Boltzmann brains problem in the framework of simple phantom energy models with little rip and big rip singularities. It is shown that these models (i) satisfy the observational data and (ii) may be free from the Boltzmann brains problem. Human observers in phantom models can exist only during a certain period t < t_f (t_f is the lifetime of the universe) via the Bekenstein bound. If the fraction of unordered observers in this part of the universe history is negligible as comparison with ordered observers, than the Boltzmann brains problem does not appear. The bounds on model parameters derived from such a requirement do not contradict to the allowable range according to the observational data.