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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2508.16530 |
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| _version_ | 1866913074268602368 |
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| author | Zhang, Feng-Yi Zhai, Rongrong Chen, Li-Yang |
| author_facet | Zhang, Feng-Yi Zhai, Rongrong Chen, Li-Yang |
| contents | We reassess single-field slow-roll inflation in teleparallel gravity with $f(T)=C\,T^{2δ+1}$, motivated by recent measurements from the Atacama Cosmology Telescope (ACT) that indicate a modest upward shift in the scalar spectral index $n_s$. Using analytic approximations together with high-precision numerical calculations, we compute primordial predictions for representative potentials: power-law monomials, hilltop models, and $E$-type plateaus. We find that torsional corrections controlled by $δ$ generically suppress $r$ while keeping $n_s$ near its slow-roll value. As a result, modest positive $δ$ can restore viability to sub-quadratic monomials and hilltop models that are disfavored in general relativity (GR), whereas $E$-type plateaus remain compatible only in a limited range of $δ$: small $δ$ may improve the fit but moderate $δ$ drives the dynamics toward quadratic-like behaviour and increases $r$. These signatures are observationally testable: improved cosmic microwave background (CMB) B-mode measurements will further discriminate among potential classes and place quantitative bounds on torsional deviations from GR. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_16530 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | ACT-Era Constraints on Single-Field Inflation in $f(T)$ Teleparallel Gravity Zhang, Feng-Yi Zhai, Rongrong Chen, Li-Yang General Relativity and Quantum Cosmology We reassess single-field slow-roll inflation in teleparallel gravity with $f(T)=C\,T^{2δ+1}$, motivated by recent measurements from the Atacama Cosmology Telescope (ACT) that indicate a modest upward shift in the scalar spectral index $n_s$. Using analytic approximations together with high-precision numerical calculations, we compute primordial predictions for representative potentials: power-law monomials, hilltop models, and $E$-type plateaus. We find that torsional corrections controlled by $δ$ generically suppress $r$ while keeping $n_s$ near its slow-roll value. As a result, modest positive $δ$ can restore viability to sub-quadratic monomials and hilltop models that are disfavored in general relativity (GR), whereas $E$-type plateaus remain compatible only in a limited range of $δ$: small $δ$ may improve the fit but moderate $δ$ drives the dynamics toward quadratic-like behaviour and increases $r$. These signatures are observationally testable: improved cosmic microwave background (CMB) B-mode measurements will further discriminate among potential classes and place quantitative bounds on torsional deviations from GR. |
| title | ACT-Era Constraints on Single-Field Inflation in $f(T)$ Teleparallel Gravity |
| topic | General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2508.16530 |