Holographic principle, cosmological constant and cyclic cosmology

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 ultraviolet (UV) and infrared (IR) cutoffs into quantum gravity which are necessarily strongly related. The equation of state for dark energy omega = p/p 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.