Holographic Entanglement Entropy in Cyclic Cosmology
  We discuss a cyclic cosmology in which the visible universe, or introverse,
is all that is accessible to an observer while the extroverse represents the
total spacetime originating from the time when the dark energy began to
dominate. It is argued that entanglement entropy of the introverse is the more
appropriate quantity to render infinitely cyclic, rather than the entropy of
the total universe. Since vanishing entanglement entropy implies disconnected
spacetimes, at the turnaround when the introverse entropy is zero the
disconnected extroverse can be jettisoned with impunity.
