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Universal nonminimal coupling-to-Starobinsky matching and a single-field attractor

A. Savaş Arapoğlu*, Sermet Çağan†, Omer Guleryuz‡, and Cemal Berfu Senisik§

  • *Contact author: arapoglu@itu.edu.tr
  • †Contact author: cagans@itu.edu.tr
  • ‡Contact author: omerguleryuz@itu.edu.tr
  • §Contact author: senisik@itu.edu.tr
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Phys. Rev. D 113, 123547 – Published 25 June, 2026

DOI: https://doi.org/10.1103/qzdk-rtk6

Abstract

We establish an off-shell commutativity theorem in 4D parity-even quadratic gravity that the Hubbard–Stratonovich/Legendre lifts, algebraic elimination of auxiliaries, including the torsionless Palatini connection, and Jordan-Einstein Weyl rescalings commute at the action level up to boundary terms. This yields a frame-independent characterization of the propagating degrees of freedom and isolates a universal scalaron EFT in the metric branch, while clarifying the algebraic nature of the Palatini f(R) scalar. We obtain, as a result, a frame-universal matching from the generic nonminimal couplings to a positive R2 sector and a quantitative single-field attractor bound, enhanced by a 1/ΔN selection term, providing sharp and falsifiable CMB targets.

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Phys. Rev. D 113, 123547– Published 25 June, 2026
  • Received 6 January 2026
  • Accepted 8 June 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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