Non-saturated holographic dark energy

It has been well established that holographic dark energy (HDE) is a serious candidate for being the dark energy of the universe. Here we deal with models where the holographic bound for dark energy is not saturated for a large portion of the history of the universe. This is particularly compelling when the IR cut-off is set by the Hubble scale, since otherwise a transition from a decelerated to an accelerated era cannot be obtained for a spatially flat universe. We demonstrate using three generic but disparate dynamical models, two of them containing a variable Newton constant, that a transition between the two eras is always obtained for the IR cut-off in the form of the Hubble scale and the non-saturated HDE. We also give arguments for why such a choice for the dark energy is more consistent and favoured over the widely accepted saturated form.