Clocking the End of Cosmic Inflation

Abstract

Making observable predictions for cosmic inflation requires determining when the wavenumbers of astrophysical interest today exited the Hubble radius during the inflationary epoch. These instants are commonly evaluated using the slow-roll approximation and measured in e-folds $\Delta N=N-N_{\mathrm{end}}$, in reference to the e-fold $N_{\mathrm{end}}$ at which inflation ended. Slow roll being necessarily violated towards the end of inflation, both the approximated trajectory and $N_{\mathrm{end}}$ are determined at, typically, one or two e-folds precision. Up to now, such an uncertainty has been innocuous, but this will no longer be the case with the forthcoming cosmological measurements. In this work, we introduce a new and simple analytical method, on top of the usual slow-roll approximation, that reduces uncertainties on $\Delta N$ to less than a tenth of an e-fold.

24 pages, 2 figures, uses jcappub. Misprints corrected, matches published version

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Cited by in corpus (4)

• Third-order corrections to the slow-roll expansion: calculation and constraints with Planck, ACT, SPT, and BICEP/Keck
• Confronting Inflation and Reheating with Observations: Improved Predictions
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• Time-reversed Stochastic Inflation