Horizon-Flow off-track for Inflation

Abstract

Inflation can be parameterized by means of truncated flow equations. In this "horizon-flow" setup, generic results have been obtained, such as typical values for $r/(1-n_{\mathrm{S}})$. They are sometimes referred to as intrinsic features of inflation itself. In this paper we first show that the phenomenological class of inflationary potentials sampled by horizon-flow is directly responsible for such predictions. They are therefore anything but generic. Furthermore, the horizon-flow setup is shown to rely on trajectories in phase space that differ from the slow-roll. For a given potential, we demonstrate that this renders horizon-flow blind to entire relevant inflationary regimes, for which the horizon-flow trajectory is shown to be unstable. This makes horizon-flow a biased parameterization of inflation.

26 pages, 20 figures. Matches published version

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• Limits on primordial power spectrum resolution: An inflationary flow analysis
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