Inflationary Models with Gauss-Bonnet Coupling in Light of ACT Observations
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| Format: | Preprint |
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2025
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| _version_ | 1866917052183216128 |
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| author | Zhu, Yigan Gao, Qing Gong, Yungui Yi, Zhu |
| author_facet | Zhu, Yigan Gao, Qing Gong, Yungui Yi, Zhu |
| contents | Recent analyses combining Atacama Cosmology Telescope (ACT) data with other cosmological datasets report a higher scalar spectral index $n_s$, creating tension with a wide range of inflationary models. Since a Gauss-Bonnet term with a coupling function $ξ(ϕ) = 3λ/[4V(ϕ)]$ leaves $n_s$ nearly unchanged (up to a field rescaling) while reducing the tensor-to-scalar ratio $r$ by a factor $(1-λ)$, so choosing $(1-λ)$ sufficiently small effectively removes $r$ as a limiting observable, making it easier for inflationary models to satisfy the latest observational constraints and alleviating this tension. Applying this mechanism to chaotic inflation, E-models, T-models, and hilltop inflation, we find that broad regions of parameter space become consistent with the latest ACT-based CMB constraints. These results demonstrate that Gauss-Bonnet couplings can help bring a broad class of inflationary models into agreement with current CMB measurements. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2508_09707 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Inflationary Models with Gauss-Bonnet Coupling in Light of ACT Observations Zhu, Yigan Gao, Qing Gong, Yungui Yi, Zhu Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology Recent analyses combining Atacama Cosmology Telescope (ACT) data with other cosmological datasets report a higher scalar spectral index $n_s$, creating tension with a wide range of inflationary models. Since a Gauss-Bonnet term with a coupling function $ξ(ϕ) = 3λ/[4V(ϕ)]$ leaves $n_s$ nearly unchanged (up to a field rescaling) while reducing the tensor-to-scalar ratio $r$ by a factor $(1-λ)$, so choosing $(1-λ)$ sufficiently small effectively removes $r$ as a limiting observable, making it easier for inflationary models to satisfy the latest observational constraints and alleviating this tension. Applying this mechanism to chaotic inflation, E-models, T-models, and hilltop inflation, we find that broad regions of parameter space become consistent with the latest ACT-based CMB constraints. These results demonstrate that Gauss-Bonnet couplings can help bring a broad class of inflationary models into agreement with current CMB measurements. |
| title | Inflationary Models with Gauss-Bonnet Coupling in Light of ACT Observations |
| topic | Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2508.09707 |