  We suggest the possibility that the mysterious dark energy component driving
the acceleration of the Universe is the leading term, in the de Sitter
temperature, of the free energy density of space-time seen as a quantum gravity
coherent state of the gravitational field. The corresponding field theory
classically has positive pressure, and can be considered as living on the
Hubble horizon, or, alternatively, within the non compact part of the
Robertson-Walker metric, both manifolds being characterized by the same scale
and degrees of freedom. The equation of state is then recovered via the
conformal anomaly. No such interpretation seems to be available for negative
{\Lambda}.
