title: Backreaction during inflation: a physical gauge invariant formulation.
abstract: 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.
authors.affiliation: INAF/IASF Bologna, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna via Gobetti 101, I-40129 Bologna, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Finelli
authors.forename: G
authors.initials: G
authors.lastname: Marozzi
authors.forename: G P
authors.initials: GP
authors.lastname: Vacca
authors.forename: G
authors.initials: G
authors.lastname: Venturi