Steps to Reconcile Inflationary Tensor and Scalar Spectra
  The recent BICEP2 B-mode polarization determination of an inflationary
tensor-scalar ratio $r=0.2^{+0.07}_{-0.05}$ is in tension with simple
scale-free models of inflation due to a lack of a corresponding low multipole
excess in the temperature power spectrum which places a limit of
$r_{0.002}<0.11$ (95% CL) on such models. Single-field inflationary models that
reconcile these two observations, even those where the tilt runs substantially,
introduce a scale into the scalar power spectrum. To cancel the tensor excess,
and simultaneously explain the excess already present in $\Lambda$CDM, ideally
the model should introduce this scale as a relatively sharp transition in the
tensor-scalar ratio around the horizon at recombination. We consider models
which generate such a step in this quantity and find that they can improve the
joint fit to the temperature and polarization data by up to $2\Delta \ln{\cal
L} \approx -14$ without changing cosmological parameters. Precision E-mode
polarization measurements should be able to test this explanation.
