Non-minimal coupling in light of ACT

2025/04/21 by Gao, Qing, Gong, Yungui, Yi, Zhu +1 · 13 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Theory (hep-th)

paper · doi:10.48550/arxiv.2504.15218

Abstract

The latest ACT data release disfavors the attractor n_s=1-2/N. In inflationary models with nonminimal coupling, such attractors typically arise in the strong coupling limit. To align with observational constraints, we focus on nonminimal coupling models with small coupling constants. For the model with the coupling function Ω(ϕ) = 1 + ξf(ϕ) and the potential V(ϕ) = λ² f²(ϕ), we find that observational data constrain the parameters as 0.1 \lesssim ξ\lesssim 35 and 0 \lesssim k \lesssim 1.5 for f(ϕ) = ϕ^k at the 1σ confidence level. With the help of the nonmiminal coupling Ω(ϕ) = 1 + ξϕ², the hilltop inflation and power-law inflation models with power indices 2/3 and 1/3 can be consistent with observational data within the 1σ range. We also give the viable parameter regions for ξ for these three models.

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