Cosmological Consequences of Initial State Entanglement
  We explore the cosmological consequences of having the fluctuations of the
inflaton field entangled with those of another scalar, within the context of a
toy model consisting of non-interacting, minimally coupled scalars in a fixed
de Sitter background. We find that despite the lack of interactions in the
Lagrangian, the initial state entanglement modifies the mode equation for the
inflaton fluctuations and thus can induce changes in cosmological observables.
These effects are examined for a variety of choices of masses and we find that
they can be consistent with the requirement that the back reaction of the
modified state not affect the inflationary phase while still giving rise to
observable effects in the power spectrum. Our results suggest that more
realistic extensions of the ideas explored here beyond the simple toy model may
lead to interesting observable effects.
