ACT-compatible Inflation in Scalar Field Coupled f(Q, R̃) Gravity
Abstract
In this work, we construct models compatible with ACT constraints on inflation in the framework of f(Q, R̃) gravity, with f(R) gravity coupled to a scalar field. The f(Q, R̃) theory is equivalent to $f(Q, B)$ gravity models or $f(Q, C)$ gravity where B or C is the difference between Q and the scalar curvature R̃ in Einstein's gravity, so, B=Q−R̃ or C=R̃ − Q. Using appropriate reconstruction techniques compatible with f(Q, R̃) theory, we propose two functional behaviors of the Hubble rate H that satisfy the constraints, and we construct models that realize these behaviors of the Hubble rate H using f(Q, R̃) gravity and f(R) gravity coupled with a scalar field. We also discuss the reheating stage after inflation. Although the scenario of f(R) gravity coupled with a scalar field is well-known, since the model can be rewritten in the form of Einstein's gravity coupled with two scalar fields, the non-trivial problem occurs in the f(Q, R̃) gravity case, because the number of dynamical degrees of freedom in f(Q) gravity is not settled.
Related
- Scalar perturbations in two-scalar-field warm inflation
- PrimordialPy: A Python library for single-field inflation, primordial black holes, and scalar-induced gravitational waves
- The alternative scalar field dark sector of the Universe: Cosmological inflation, quintessence and ekpyrotic model in the framework of scalar-tensor cosmology
- Conformally Coupled Scalar- Field Dark Energy: Cosmological Dynamics with Early- and Late- Measurements
- Reconciling nonminimally coupled Higgs inflation with ACT DR6 observations through reheating
BibTeX
@misc{nojiri2026actcompatible,
title = {{ACT-compatible Inflation in Scalar Field Coupled $f\left(Q, \tilde R\right)$ Gravity}},
author = {Shin'ichi Nojiri and S. D. Odintsov and V. K. Oikonomou},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.23511},
eprint = {2609.23511},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.23511},
}
RIS
TY - UNPB
TI - ACT-compatible Inflation in Scalar Field Coupled f(Q, R̃) Gravity
AU - Shin'ichi Nojiri
AU - S. D. Odintsov
AU - V. K. Oikonomou
PY - 2026
DA - 2026/09/20
PB - arXiv
DO - 10.48550/arxiv.2609.23511
UR - https://arxiv.org/abs/2609.23511
AB - In this work, we construct models compatible with ACT constraints on inflation in the framework of f(Q, R̃) gravity, with f(R) gravity coupled to a scalar field. The f(Q, R̃) theory is equivalent to $f(Q, B)$ gravity models or $f(Q, C)$ gravity where B or C is the difference between Q and the scalar curvature R̃ in Einstein's gravity, so, B=Q−R̃ or C=R̃ − Q. Using appropriate reconstruction techniques compatible with f(Q, R̃) theory, we propose two functional behaviors of the Hubble rate H that satisfy the constraints, and we construct models that realize these behaviors of the Hubble rate H using f(Q, R̃) gravity and f(R) gravity coupled with a scalar field. We also discuss the reheating stage after inflation. Although the scenario of f(R) gravity coupled with a scalar field is well-known, since the model can be rewritten in the form of Einstein's gravity coupled with two scalar fields, the non-trivial problem occurs in the f(Q, R̃) gravity case, because the number of dynamical degrees of freedom in f(Q) gravity is not settled.
ER -