A new model of agegraphic dark energy

In this note, we propose a new model of agegraphic dark energy based on the Károlyházy relation, where the time scale is chosen to be the conformal time η of the Friedmann Robertson Walker (FRW) universe. We find that in the radiation-dominated epoch, the equation-of-state parameter of the new agegraphic dark energy w=-1/3 whereas Ω=na; in the matter-dominated epoch, w=-2/3 whereas Ω=na/4; eventually, the new agegraphic dark energy dominates; in the late time w→-1 when a→∞, and the new agegraphic dark energy mimics a cosmological constant. In every stage, all things are consistent. The confusion in the original agegraphic dark energy model proposed in [R.G. Cai, Phys. Lett. B 657 (2007) 228, arXiv: 0707.4049 [hep-th]] disappears in this new model. Furthermore, Ω≪1 is naturally satisfied in both radiation-dominated and matter-dominated epochs where a≪1. In addition, we further extend the new agegraphic dark energy model by including the interaction between the new agegraphic dark energy and background matter. In this case, we find that w can cross the phantom divide.