Conformal frames in cosmology
  From higher dimensional theories, e.g. string theory, one expects the
presence of non-minimally coupled scalar fields. We review the notion of
conformal frames in cosmology and emphasize their physical equivalence, which
holds at least at a classical level.
  Furthermore, if there is a field, or fields, which dominates the universe, as
it is often the case in cosmology, we can use such notion of frames to treat
our system, matter and gravity, as two different sectors. On one hand, the
gravity sector which describes the dynamics of the geometry and on the other
hand the matter sector which has such geometry as a playground. We use this
interpretation to build a model where the fact that a curvaton couples to a
particular frame metric could leave an imprint in the CMB.
