Linking the BICEP2 result and the hemispherical power asymmetry through
  spatial variation of $r$
  For the simplest inflation models, the recent detection of a large primordial
B-mode polarization signal by the BICEP2 experiment indicates a slight tension
with the upper limit on the tensor-to-scalar ratio, $r$, from the Planck
satellite. Here, we discuss spatially varying $r$ as a possible explanation for
this discrepancy. This idea seems attractive since it may also explain part of
the hemispherical temperature power asymmetry seen by WMAP and Planck at large
angular scales. If these two aspects are indeed connected, the model suggests
that in the Northern hemisphere $r$ should be much smaller, a hypothesis that
could be confirmed with future B-mode experiments, providing a test for the
stationarity of primordial tensor contributions across the sky. The BICEP2
measurement furthermore rules out that a simple dipolar modulation of $r$ alone
can be responsible for the full hemispherical power asymmetry.
