2024/10/15 by Eugenio Bianchi, Bianchi, Eugenio, Mauricio Gamonal +1
Earth and Planetary Sciences · Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Geophysics and Gravity Measurements #High Energy Physics - Theory (hep-th) #Solar and Space Plasma Dynamics
paper · pdf · doi:10.48550/arxiv.2410.11812
openalex publication_date 2024/10/15 · openalex created_date 2024/10/20 · openalex updated_date 2026/08/01
A finite duration of cosmic inflation can result in features PR(k) = |αk-βk eiδk|2 PR(0)(k) in the primordial power spectrum that carry information about a quantum gravity phase before inflation. While the almost scale-invariant power spectrum PR(0) for the quasi-Bunch-Davies vacuum is fully determined by the inflationary background dynamics, the Bogoliubov coefficients αk and βk for the squeezed vacuum depend on new physics beyond inflation and have been used to produce phenomenological templates for the features. The phase δk vanishes in de Sitter space and therefore is often neglected, but it results in non-trivial effects in quasi-de Sitter inflationary geometries. Here we consider a large class of effective theories of inflation and provide a closed-form expression for δk and for the fully expanded power spectrum up to next-to-next-leading order (N2LO) in the Hubble-flow expansion. In particular, for the Starobinsky model of inflation we find that this relative phase can be expressed in terms of the scalar tilt ns as δk∗=\fracπ2(ns-1)-\fracπ4(ns-1)2 ln(k/k_*). The relative phase results in a negative shift and a running frequency that have been considered in the most studied phenomenological templates for primordial features, thus providing precise theoretical predictions for upcoming cosmological observations.