Multi-field inflation from single-field models
  Quantization implies independent degrees of freedom that do not appear in the
classical theory, given by fluctuations, correlations, and higher moments of a
state. A systematic derivation of the resulting dynamical systems is presented
here in a cosmological application for near-Gaussian states of a single-field
inflation model. As a consequence, single-field Higgs inflation is made viable
observationally by becoming a multi-field model with a specific potential for a
fluctuation field interacting with the inflaton expectation value. Crucially,
non-adiabatic methods of semiclassical quantum dynamics reveal important phases
that can set suitable initial conditions for slow-roll inflation (in
combination with the uncertainty relation), and then end inflation after the
observationally preferred number of e-folds. New parameters in the interaction
potential are derived from properties of the underlying background state,
demonstrating how background non-Gaussianity can affect observational features
of inflation or, conversely, how observations may be used to understand the
quantum state of the inflaton.
