Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT
Recent measurements from the Atacama Cosmology Telescope (ACT), combined with Planck and DESI data, suggest a higher value for the spectral index ns. This places Starobinsky inflation at the edge of the 2σ constraints for a number of e-folds N⋆ around 60 when using the usual analytical approximation...
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Elsevier
2025-08-01
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| Series: | Physics Letters B |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0370269325003739 |
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| author | Manuel Drees Yong Xu |
| author_facet | Manuel Drees Yong Xu |
| author_sort | Manuel Drees |
| collection | DOAJ |
| description | Recent measurements from the Atacama Cosmology Telescope (ACT), combined with Planck and DESI data, suggest a higher value for the spectral index ns. This places Starobinsky inflation at the edge of the 2σ constraints for a number of e-folds N⋆ around 60 when using the usual analytical approximations. We present refined predictions for Starobinsky inflation that go beyond the commonly used analytical approximations. By evaluating the model with these improved expressions, we show that for N⋆≳58 it remains consistent with current observational constraints at the 2σ level. Additionally, we examine the implications of the ACT results for post-inflationary reheating parameters. Specifically, we find a lower bound on the effective equation of state parameter during reheating of approximately ω≳0.462; this excludes purely perturbative reheating, which leads to ω≃0. We also show that the reheating temperature is constrained to be Trh≲2×1010GeV, assuming ω≤1. Furthermore, we find that the predictions for the spectral index and tensor-to-scalar ratio can lie within 1σ of the recent ACT constraints if the reheating temperature satisfies 4MeV≲Trh≲10GeV for 0.8≲ω≤1. |
| format | Article |
| id | doaj-art-e30e046e159a4064936652e8c2a046cf |
| institution | DOAJ |
| issn | 0370-2693 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Physics Letters B |
| spelling | doaj-art-e30e046e159a4064936652e8c2a046cf2025-08-20T03:07:24ZengElsevierPhysics Letters B0370-26932025-08-0186713961210.1016/j.physletb.2025.139612Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACTManuel Drees0Yong Xu1Bethe Center for Theoretical Physics and Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, GermanyPRISMA+ Cluster of Excellence and Mainz Institute for Theoretical Physics, Johannes Gutenberg University, 55099 Mainz, Germany; Corresponding author.Recent measurements from the Atacama Cosmology Telescope (ACT), combined with Planck and DESI data, suggest a higher value for the spectral index ns. This places Starobinsky inflation at the edge of the 2σ constraints for a number of e-folds N⋆ around 60 when using the usual analytical approximations. We present refined predictions for Starobinsky inflation that go beyond the commonly used analytical approximations. By evaluating the model with these improved expressions, we show that for N⋆≳58 it remains consistent with current observational constraints at the 2σ level. Additionally, we examine the implications of the ACT results for post-inflationary reheating parameters. Specifically, we find a lower bound on the effective equation of state parameter during reheating of approximately ω≳0.462; this excludes purely perturbative reheating, which leads to ω≃0. We also show that the reheating temperature is constrained to be Trh≲2×1010GeV, assuming ω≤1. Furthermore, we find that the predictions for the spectral index and tensor-to-scalar ratio can lie within 1σ of the recent ACT constraints if the reheating temperature satisfies 4MeV≲Trh≲10GeV for 0.8≲ω≤1.http://www.sciencedirect.com/science/article/pii/S0370269325003739 |
| spellingShingle | Manuel Drees Yong Xu Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT Physics Letters B |
| title | Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT |
| title_full | Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT |
| title_fullStr | Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT |
| title_full_unstemmed | Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT |
| title_short | Refined predictions for Starobinsky inflation and post-inflationary constraints in light of ACT |
| title_sort | refined predictions for starobinsky inflation and post inflationary constraints in light of act |
| url | http://www.sciencedirect.com/science/article/pii/S0370269325003739 |
| work_keys_str_mv | AT manueldrees refinedpredictionsforstarobinskyinflationandpostinflationaryconstraintsinlightofact AT yongxu refinedpredictionsforstarobinskyinflationandpostinflationaryconstraintsinlightofact |