Investigating f(R)-inflation: Background evolution and constraints

Journal of Cosmology and Astroparticle Physics, vol. 2026, pp. 006

Abstract

Abstract In this work, we investigate the possibility of generating an inflationary mechanism within the framework of a metric- f ( R ) modified gravity theory, formulated in the Jordan frame. We explore whether the scalar field, non-minimally coupled to gravity and emerging in the Jordan frame, can play the role of the primordial inflaton. Particular attention is devoted to constructing a dynamical scenario in the Jordan frame that exhibits a slow-rolling phase for the scalar field and admits a quasi-de Sitter solution for cosmic evolution. To ensure consistency with the standard cosmological model, we impose a matching condition with the ΛCDM model at the end of the inflationary phase. Furthermore, to address the problem of the absence of matter after inflation, we consider a radiation-type particle creation process that maintains an approximately constant energy density. We test our theoretical model against background observational data, specifically Pantheon + calibrated with SH0ES and DESI calibrated with BBN. We asses the model's viability by combining theoretical consistency tests with its predictions for primordial power spectrum observables, and we discuss the implications for alleviating the Hubble constant tension.

Authors 5

1. Elisa Fazzari

   Sapienza University of Rome · University of Rome Tor Vergata · Istituto Nazionale di Fisica Nucleare, Sezione di Roma I

   Affiliation as printed

   Physics Department, INFN — Sezione di Roma, P.le A. Moro 5, I-00185, Roma,

   Physics Department, Sapienza University of Rome, P.le A. Moro 5, 00185 Roma,

   Physics Department, Tor Vergata University of Rome, Via della Ricerca Scientifica 1, Roma, 00133,

2. Giovanni Montani

   Sapienza University of Rome · National Agency for New Technologies, Energy and Sustainable Economic Development · ENEA Frascati Research Centre

   Affiliation as printed

   Nuclear Department, ENEA — C.R. Frascati, Via E. Fermi 45, 00044 Frascati,

   Physics Department, Sapienza University of Rome, P.le A. Moro 5, 00185 Roma,

3. M. Martinelli

   National Institute for Astrophysics · Istituto Nazionale di Fisica Nucleare, Sezione di Roma I · Astronomical Observatory of Rome

   Affiliation as printed

   INAF — Osservatorio Astronomico di Roma, via Frascati 33, 00078 Monte Porzio Catone,

   Physics Department, INFN — Sezione di Roma, P.le A. Moro 5, I-00185, Roma,

4. ALESSANDRO MELCHIORRI

   Sapienza University of Rome · Istituto Nazionale di Fisica Nucleare, Sezione di Roma I

   Affiliation as printed

   Physics Department, INFN — Sezione di Roma, P.le A. Moro 5, I-00185, Roma,

   Physics Department, Sapienza University of Rome, P.le A. Moro 5, 00185 Roma,

5. G Cañas-Herrera Aachen Leiden Observatory

   Leiden University · European Space Agency · Leiden Observatory · European Space Research and Technology Centre

   Affiliation as printed

   ESTEC — European Space Agency, Keplerlaan 1, 2201 AZ Noordwijk,

   Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden,