Holographic principle and dark energy

We discuss the relationship between holographic entropy bounds and gravitating systems. In order to obtain a holographic energy density, we introduce the Bekenstein-Hawking entropy SBH and its corresponding energy EBH using the Friedman equation. We show that the holographic energy bound proposed by Cohen et al. comes from the Bekenstein-Hawking bound for a weakly gravitating system. Also we find that the holographic energy density with the future event horizon deriving an accelerating universe could be given by vacuum fluctuations of the energy density.