Inflation After False Vacuum Decay: New Evidence from BICEP2
  Last year we argued that if slow-roll inflation followed the decay of a false
vacuum in a large landscape, the steepening of the scalar potential between the
inflationary plateau and the barrier generically leads to a potentially
observable suppression of the scalar power spectrum at large distances. Here we
revisit this analysis in light of the recent BICEP2 results. Assuming that both
the BICEP2 B-mode signal and the Planck analysis of temperature fluctuations
hold up, we find that the data now discriminate more sharply between our
scenario and $\Lambda$CDM. Nonzero tensor modes exclude standard $\Lambda$CDM
with notable but not yet conclusive confidence: at $\sim 3.8\,\sigma$ if
$r\approx0.2$, or at $\sim 3.5\,\sigma$ if $r=0.15$. Of the two steepening
models of our previous work, one is now ruled out by existing bounds on spatial
curvature. The other entirely reconciles the tension between BICEP2 and Planck.
Upcoming $EE$ polarization measurements have the potential to rule out
unmodified $\Lambda$CDM decisively. Next generation Large Scale Structure
surveys can further increase the significance. More precise measurements of
$BB$ at low $\ell$ will help distinguish our scenario from other explanations.
If steepening is confirmed, the prospects for detecting open curvature increase
but need not be large.
