Observable effects of anisotropic bubble nucleation
  Our universe may have formed via bubble nucleation in an eternally-inflating
background. Furthermore, the background may have a compact dimension--the
modulus of which tunnels out of a metastable minimum during bubble
nucleation--which subsequently grows to become one of our three large spatial
dimensions. Then the reduced symmetry of the background is equivalent to
anisotropic initial conditions in our bubble universe. We compute the
inflationary spectrum in such a scenario and, as a first step toward
understanding the effects of anisotropy, project it onto spherical harmonics.
The resulting spectrum exhibits anomalous multipole correlations, their
relative amplitude set by the present curvature parameter, which extend to
arbitrarily large multipole moments. This raises the possibility of future
detection, if slow-roll inflation does not last too long within our bubble. A
full understanding of the observational signal must account for the effects of
background anisotropy on photon free streaming, and is left to future work.
