A New Model of Agegraphic Dark Energy

In this note, we propose a new model of agegraphic dark energy based on the K\'{a}rolyh\'{a}zy relation, where the time scale is chosen to be the conformal time $\eta$ 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 $w_q=-1/3$ whereas $\Omega_q=n^2a^2$; in the matter-dominated epoch, $w_q=-2/3$ whereas $\Omega_q=n^2a^2/4$; eventually, the new agegraphic dark energy dominates; in the late time $w_q\to -1$ when $a\to\infty$, 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 arXiv:0707.4049 disappears in this new model. Furthermore, $\Omega_q\ll 1$ is naturally satisfied in both radiation-dominated and matter-dominated epochs where $a\ll 1$. 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 $w_q$ can cross the phantom divide.