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  • Open Access

Unitarization of R+αR2 gravity

Iñigo Asiáin1,*, Antonio Dobado2,†, and Domènec Espriu1,‡

  • *Contact author: iasiain@icc.ub.edu
  • †Contact author: dobado@fis.ucm.es
  • ‡Contact author: espriu@icc.ub.edu
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Phys. Rev. D 113, 086012 – Published 30 April, 2026

DOI: https://doi.org/10.1103/w5z3-3nkm

Abstract

We make use of the improved K-matrix algorithm to obtain unitarized amplitudes in R+αR2 gravity (the so-called Starobinsky model, of cosmological relevance). The procedure is of some complexity because infrared divergences are present and need to be properly regulated. We focus on the behavior of a bona fide scalar resonance, known to exist in this model, and compare it to an apparent resonance detected in previous studies, thus confirming that the latter seems to be an artifact due to the introduction of the infrared regulator. We analyze the existence of other dynamical resonances and dwell on the amplitudes made unitary by this procedure.

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Phys. Rev. D 113, 086012– Published 30 April, 2026
  • Received 22 December 2025
  • Accepted 23 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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