2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/201084We study the WKB approximation beyond leading order for cosmological perturbations during inflation. To first order in the slow-roll parameters, we show that an improved WKB approximation leads to analytical results agreeing to within 0.1% with the standard slow-roll results. Moreover, the leading WKB approximation to second order in the slow-roll parameters leads to analytical predictions in qualitative agreement with those obtained by the Green's function method.Replaced to match published versionGeneral Relativity and Quantum CosmologyAstrophysicsHigh Energy Physics - Theorytext