On the number of e-folds in the Jordan and Einstein frames
National Institute of Chemical Physics and Biophysics, Rävala 10, 10143, Tallinn, Estonia
2 Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411, Tartu, Estonia
Accepted: 19 May 2022
Published online: 30 May 2022
We investigate how inflationary predictions are affected by the difference in the number of e-folds between the Jordan and Einstein frames. We study several test models in relation to a Jordan frame defined by the common Higgs-inflation-like non-minimal coupling to gravity and consider two different formulations of gravity: metric and Palatini. We find that the difference is quite contained in case of a metric Jordan frame while can be quite remarkable in case of a Palatini Jordan frame. We also discuss a way to overcome the discrepancy by using a frame invariant physical distance and a consequently frame invariant number of e-folds.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2022