The MESS of the CMB
  We analyze cosmic microwave background (CMB) data taking into account the
effects of a momentum dependent effective sound speed (MESS). This approach
allows to study the effects of primordial entropy in a model independent way,
and its implementation requires a minimal modification of existing CMB fitting
numerical codes developed for single scalar field models.
  We adopt a phenomenological approach, and study the effects a local variation
of the MESS around the scale where other analysis have shown some deviation
from an approximately scale invariant curvature perturbation spectrum. We
obtain a substantial improvement of the fit with respect to a model without
MESS, showing that primordial entropy modeled by MESS can be an explanation of
these deviations.
