Backreaction during inflation: a physical gauge invariant formulation
  Within a genuinely gauge invariant approach recently developed for the
computation of the cosmological backreaction, we study, in a cosmological
inflationary context and with respect to various observers, the impact of
scalar fluctuations on the space-time dynamics in the long wavelength limit. We
stress that such a quantum backreaction effect is evaluated in a truly gauge
independent way using a set of effective equations which describe the dynamics
of the averaged geometry. In particular we show under what conditions the free
falling (geodetic) observers do not experience any scalar-induced backreaction
in the effective Hubble rate and fluid equation of state.
