Reviving Motivated Inflationary Potentials with $K$-inflation in the light of ACT
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2026
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| author | Solbi, Milad Samart, Daris Simakachorn, Peera |
| author_facet | Solbi, Milad Samart, Daris Simakachorn, Peera |
| contents | Recent ACT data favor a higher scalar spectral index $n_s$, placing models such as $α$-attractor T-models and natural Inflation in tension with current observations. We propose a K-inflation framework with a field-dependent non-canonical kinetic term $G(ϕ)$ that reconciles these models with the latest Planck-ACT-LB-BK18 constraints. Our analysis includes a refined calculation of the reheating equation-of-state parameter $w_{\rm re}$, avoids standard power-law approximations, and tests consistency with the Swampland Distance and de Sitter Conjectures. We find that the additional friction from the non-minimal kinetic coupling shifts both models into the favored observational regions. For the $α$-attractor T-model with $n=2$, viable solutions occur for $β\sim \mathcal{O}(10)$, with Swampland consistency favoring $α\gtrsim \mathcal{O}(10^{-3})$. This case predicts matter-like reheating and a red-tilted gravitational-wave background that is unlikely to be detected soon. In contrast, natural Inflation with $n=4,5$ is compatible with CMB constraints for $α\lesssim 7,8$ and $β\lesssim -1$, respectively, leading to stiff reheating and a blue-tilted gravitational-wave background potentially observable by LISA, Cosmic Explorer, Einstein Telescope, DECIGO, and BBO while satisfying BBN and $ΔN_{\rm eff}$ bounds. Combining gravitational-wave probes with Swampland criteria may therefore help distinguish possible UV completions of inflation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_01992 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Reviving Motivated Inflationary Potentials with $K$-inflation in the light of ACT Solbi, Milad Samart, Daris Simakachorn, Peera General Relativity and Quantum Cosmology Cosmology and Nongalactic Astrophysics Recent ACT data favor a higher scalar spectral index $n_s$, placing models such as $α$-attractor T-models and natural Inflation in tension with current observations. We propose a K-inflation framework with a field-dependent non-canonical kinetic term $G(ϕ)$ that reconciles these models with the latest Planck-ACT-LB-BK18 constraints. Our analysis includes a refined calculation of the reheating equation-of-state parameter $w_{\rm re}$, avoids standard power-law approximations, and tests consistency with the Swampland Distance and de Sitter Conjectures. We find that the additional friction from the non-minimal kinetic coupling shifts both models into the favored observational regions. For the $α$-attractor T-model with $n=2$, viable solutions occur for $β\sim \mathcal{O}(10)$, with Swampland consistency favoring $α\gtrsim \mathcal{O}(10^{-3})$. This case predicts matter-like reheating and a red-tilted gravitational-wave background that is unlikely to be detected soon. In contrast, natural Inflation with $n=4,5$ is compatible with CMB constraints for $α\lesssim 7,8$ and $β\lesssim -1$, respectively, leading to stiff reheating and a blue-tilted gravitational-wave background potentially observable by LISA, Cosmic Explorer, Einstein Telescope, DECIGO, and BBO while satisfying BBN and $ΔN_{\rm eff}$ bounds. Combining gravitational-wave probes with Swampland criteria may therefore help distinguish possible UV completions of inflation. |
| title | Reviving Motivated Inflationary Potentials with $K$-inflation in the light of ACT |
| topic | General Relativity and Quantum Cosmology Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2605.01992 |