posted on 2023-06-08, 22:37authored byMafalda Dias, Joseph Elliston, Jonathan Frazer, David Mulryne, David SeeryDavid Seery
We give an explicit relation, up to second-order terms, between scalar-field fluctuations defined on spatially-flat slices and the curvature perturbation on uniform-density slices. This expression is a necessary ingredient for calculating observable quantities at second-order and beyond in multiple-field inflation. We show that traditional cosmological perturbation theory and the `separate universe' approach yield equivalent expressions for superhorizon wavenumbers, and in particular that all nonlocal terms can be eliminated from the perturbation-theory expressions.
Funding
Precisions tests of the inflationary scenario; G0918; EUROPEAN UNION; 308082