The Multiverse in an Inverted Island
  We study the redundancies in the global spacetime description of the
eternally inflating multiverse using the quantum extremal surface prescription.
We argue that a sufficiently large spatial region in a bubble universe has an
entanglement island surrounding it. Consequently, the semiclassical physics of
the multiverse, which is all we need to make cosmological predictions, can be
fully described by the fundamental degrees of freedom associated with certain
finite spatial regions. The island arises due to mandatory collisions with
collapsing bubbles, whose big crunch singularities indicate redundancies of the
global spacetime description. The emergence of the island and the resulting
reduction of independent degrees of freedom provides a regularization of
infinities which caused the cosmological measure problem.
