Gauge Invariance, Polar Coordinates and Inflation
  We point out the necessity of resolving the apparent gauge dependence in the
quantum corrections of cosmological observables for Higgs-like inflation
models. We highlight the fact that this gauge dependence is due to the use of
an asymmetric background current which is specific to a choice of coordinate
system in the scalar manifold. Favoring simplicity over complexity, we further
propose a practical shortcut to gauge-independent inflationary observables by
using effective potential obtained from a polar-like background current choice.
We demonstrate this shortcut for several explicit examples and present a
gauge-independent prediction of inflationary observables in the Abelian Higgs
model. Furthermore, with Nielsen's gauge dependence identities, we show that
for any theory to all orders, a gauge-invariant current term gives a
gauge-independent effective potential and thus gauge-invariant inflationary
observables.
