Classical Entanglement Structure in the Wavefunction of Inflationary
  Fluctuations
  We argue that the preferred classical variables that emerge from a pure
quantum state are determined by its entanglement structure in the form of
redundant records: information shared between many subsystems. Focusing on the
early universe, we ask how classical metric perturbations emerge from vacuum
fluctuations in an inflationary background. We show that the squeezing of the
quantum state for super-horizon modes, along with minimal gravitational
interactions, leads to decoherence and to an exponential number of records of
metric fluctuations on very large scales, $\lambda/\lambda_{\rm
Hubble}>\Delta_\zeta^{-2/3}$, where $\Delta_\zeta\lesssim 10^{-5}$ is the
amplitude of scalar metric fluctuations. This determines a preferred
decomposition of the inflationary wavefunction into orthogonal "branches"
corresponding to classical metric perturbations, which defines an inflationary
entropy production rate and accounts for the emergence of stochastic,
inhomogeneous spacetime geometry.
