Dark energy from entanglement entropy
  We show that quantum decoherence, in the context of observational cosmology,
can be connected to the cosmic dark energy. The decoherence signature could be
characterized by the existence of quantum entanglement between cosmological
eras. As a consequence, the Von Neumann entropy related to the entanglement
process, can be compared to the thermodynamical entropy in a homogeneous and
isotropic universe. The corresponding cosmological models are compatible with
the current observational bounds being able to reproduce viable equations of
state without introducing {\it a priori} any cosmological constant. In doing
so, we investigate two cases, corresponding to two suitable cosmic volumes,
$V\propto a^3$ and $V\propto H^{-3}$, and find two models which fairly well
approximate the current cosmic speed up. The existence of dark energy can be
therefore reinterpreted as a quantum signature of entanglement, showing that
the cosmological constant represents a limiting case of a more complicated
model derived from the quantum decoherence.
