The holographic principle provides a deep insight into quantum gravity and resolves the fine-tuning crisis concerning the cosmological constant .
Holographic dark energy introduces new ultra-violet ( UV ) and infra-red ( IR ) cutoffs into quantum gravity which are necessarily strongly related .
The equation of state for dark energy \omega = p / \rho is discussed from the holographic point of view .
The phantom option of \omega < -1 is resurrected , as in an earlier cyclic cosmology .
Such a cyclic model can , however , equally use the cosmological constant with \omega = -1 .