Vanilla inflation predicts negative running

Jérôme Martin; Christophe Ringeval; Vincent Vennin

doi:10.1209/0295-5075/ad847c

All issues

Volume 148 / No 2 (October 2024)

EPL, 148 2 (2024) 29002

Abstract

Issue		EPL Volume 148, Number 2, October 2024


Article Number		29002
Number of page(s)		5
Section		Gravitation, cosmology and astrophysics
DOI		https://doi.org/10.1209/0295-5075/ad847c
Published online		22 October 2024

EPL, 148 (2024) 29002

Vanilla inflation predicts negative running

Jérôme Martin¹ (jmartin@iap.fr), Christophe Ringeval²^,1 (christophe.ringeval@uclouvain.be) and Vincent Vennin³^,1 (vincent.vennin@ens.fr)

¹ Institut d'Astrophysique de Paris - 98bis boulevard Arago, 75014 Paris, France
² Cosmology, Universe and Relativity at Louvain (CURL), Institute of Mathematics and Physics, University of Louvain - 2 Chemin du Cyclotron, 1348 Louvain-la-Neuve, Belgium
³ Laboratoire de Physique de l’École Normale Supérieure, ENS, CNRS, Université PSL, Sorbonne Université, Université Paris Cité - 75005 Paris, France

Received: 17 July 2024
Accepted: 8 October 2024

Abstract

We show that the simplest, and currently favoured, theoretical realizations of cosmic inflation yield a sharp prediction for the running of the spectral index $\alpha _{{\textrm {s}}}$ . Using latest cosmological data, we compute its marginalized posterior probability distribution over the space of nearly 300 models of single-field slow-roll inflation. The most probable value is $\alpha _{{\textrm {s}}}=-6.3\,\times10^{-4}$ , lying within the $98\,\%$ credible interval $-1.8\,\times10^{-3}<\alpha _{{\textrm {s}}}< -9.1\,\times10^{-5}$ . Within the landscape of all the proposed slow-roll inflationary models, positive values for the running are therefore disfavoured at more than three-sigma.

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