Non-Gaussian and loop effects of inflationary correlation functions in
  BRST formalism
  We investigate inflationary correlation functions in single field inflation
models. We adopt a BRST formalism where locality and covariance at the
sub-horizon scale are manifest. The scalar and tensor perturbations are
identified with those in the comoving gauge which become constant outside the
cosmological horizon. Our construction reproduces the identical non-Gaussianity
with the standard comoving gauge. The accumulation of almost scale invariant
fluctuations could give rise to IR logarithmic corrections at the loop level.
We investigate the influence of this effect on the sub-horizon dynamics. Since
such an effect must respect covariance, our BRST gauge has an advantage over
the standard comoving gauge. We estimate IR logarithmic effects to the
slow-roll parameters at the one-loop level. We show that $\epsilon$ receives IR
logarithmic corrections, while this is not the case for $\eta$. We point out
that IR logarithmic effects provide the shift symmetry breaking mechanism. This
scenario may lead to an inflation model with a linear potential.
