Compatibility of Planck and BICEP2 in the Light of Inflation
  We investigate the implications for inflation of the detection of B-modes
polarization in the Cosmic Microwave Background (CMB) by BICEP2. We show that
the hypothesis of primordial origin of the measurement is only favored by the
first four bandpowers, while the others would prefer unreasonably large values
of the tensor-to-scalar ratio. Using only those four bandpowers, we carry out a
complete analysis in the cosmological and inflationary slow-roll parameter
space using the BICEP2 polarization measurements alone and extract the Bayesian
evidences and complexities for all the Encyclopaedia Inflationaris models. This
allows us to determine the most probable and simplest BICEP2 inflationary
scenarios. Although this list contains the simplest monomial potentials, it
also includes many other scenarios, suggesting that focusing model building
efforts on large field models only is unjustified at this stage. We demonstrate
that the sets of inflationary models preferred by Planck alone and BICEP2 alone
are almost disjoint, indicating a clear tension between the two data sets. We
address this tension with a Bayesian measure of compatibility between BICEP2
and Planck. We find that for models favored by Planck the two data sets tend to
be incompatible, whereas there is a moderate evidence of compatibility for the
BICEP2 preferred models. As a result, it would be premature to draw any
conclusion on the best Planck models, such as Starobinsky and/or Kahler moduli
inflation. For the subset of scenarios not exhibiting data sets
incompatibility, we update the evidences and complexities using both data sets
together.
