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 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 $\omega = -1$.
