Primordial Anisotropies in Gauged Hybrid Inflation
  We study primordial anisotropies generated in the model of gauged hybrid
inflation in which the complex waterfall field is charged under a $U(1)$ gauge
field. Primordial anisotropies are generated either actively during inflation
or from inhomogeneities modulating the surface of end of inflation during
waterfall transition. We present a consistent $\delta N$ mechanism to calculate
the anisotropic power spectrum and bispectrum. We show that the primordial
anisotropies generated at the surface of end of inflation do not depend on the
number of e-folds and therefore do not produce dangerously large anisotropies
associated with the IR modes. Furthermore, one can find the parameter space
that the anisotropies generated from the surface of end of inflation cancel the
anisotropies generated during inflation, therefore relaxing the constrains on
model parameters imposed from IR anisotropies. We also show that the gauge
field fluctuations induce a red-tilted power spectrum so the averaged power
spectrum from the gauge field can change the total power spectrum from blue to
red. Therefore, hybrid inflation, once gauged under a $U(1)$ field, can be
consistent with the cosmological observations.
