A confirmation of agreement of different approaches for scalar gauge-invariant metric perturbations during inflation

摘要

We revisit an extension of the well-known for_malism for gauge-invariant scalar metric fluctuations to study the spectra for both the inflaton and gauge-invariant (scalar) metric fluctuations in the framework of a single-field inflationary model, in which the quasi-exponential expan_sion is driven by an inflaton which is minimally coupled to gravity. The proposal here examined is valid also for fluc_tuations with large amplitudes, but for cosmological scales, where vector and tensor perturbations can be neglected and the fluid is irrotacional.