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R2-Higgs inflation: R3 contribution and preheating after ACT and SPT data

Tanmoy Modak

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Phys. Rev. D 112, 115006 – Published 1 December, 2025

DOI: https://doi.org/10.1103/srpt-jd6s

Abstract

The R2-Higgs inflation is one of the simplest yet best-fit models consistent with Planck data. The higher spectral index ns recently reported by the combined cosmic microwave background (CMB) data from the Atacama Cosmology Telescope (ACT), South Pole Telescope (SPT), and Planck, along with baryonic acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI), disfavors the single-field-like regime of R2-Higgs inflation at approximately 2σ. Following a doubly covariant formalism, we show that the R2-Higgs inflation, when modified by a dimension-six R3 term, can account for the high ns reported by CMB+BAO. In this regard, we find that preheating may play a pivotal role. We also show that if the nonminimal coupling between the Ricci scalar R and the Higgs field is O(10), then preheating via the production of Higgs quanta may help explain the reported observations.

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Phys. Rev. D 112, 115006– Published 1 December, 2025
  • Received 8 September 2025
  • Accepted 30 October 2025
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