Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data

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Autori principali: Ellis, John, Garcia, Marcos A. G., Olive, Keith A., Verner, Sarunas
Natura: Preprint
Pubblicazione: 2025
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author Ellis, John
Garcia, Marcos A. G.
Olive, Keith A.
Verner, Sarunas
author_facet Ellis, John
Garcia, Marcos A. G.
Olive, Keith A.
Verner, Sarunas
contents We analyze the latest cosmic microwave background (CMB) constraints on the scalar spectral index $n_s$ and tensor-to-scalar ratio $r$ from Planck 2018, BICEP/Keck 2018, the Atacama Cosmology Telescope Data Release 6 (ACT DR6), and the South Pole Telescope (SPT-3G) data, focusing on their implications for attractor models of inflation. We compare systematically observational bounds with theoretical predictions for both E-model ($α$-Starobinsky) and T-model potentials. The observational constraints accommodate E-models with $α\lesssim 25$, with the canonical Starobinsky model ($α= 1$) predicting $n_s = 0.958-0.963$ for reheating temperatures between $100 - 10^{10}$ GeV, in good agreement with Planck 2018 data and within the 95% CL region determined by the Planck-ACT-SPT combination, but below the 95% confidence region of the Planck-ACT-DESI combination. Higher reheating temperatures from near-instantaneous reheating improve the compatibility. T-models predict slightly lower $n_s$ values (0.956-0.961), in some tension with Planck 2018 data, and we find an upper limit of $α\lesssim 11$ in these models. We extend our analysis to generalized $α$-attractors with monomial potentials $V(φ) \propto φ^k$ near the minimum, demonstrating that models with $k \geq 6$ naturally predict $n_s \simeq 0.965 - 0.968$ for typical number of $e$-folds, in better agreement with the ACT DR6 data. We also consider deformed E- and T-models, which allow significantly higher values of $n_s$ for low values of $α\simeq 1$.
format Preprint
id arxiv_https___arxiv_org_abs_2510_18656
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data
Ellis, John
Garcia, Marcos A. G.
Olive, Keith A.
Verner, Sarunas
High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
We analyze the latest cosmic microwave background (CMB) constraints on the scalar spectral index $n_s$ and tensor-to-scalar ratio $r$ from Planck 2018, BICEP/Keck 2018, the Atacama Cosmology Telescope Data Release 6 (ACT DR6), and the South Pole Telescope (SPT-3G) data, focusing on their implications for attractor models of inflation. We compare systematically observational bounds with theoretical predictions for both E-model ($α$-Starobinsky) and T-model potentials. The observational constraints accommodate E-models with $α\lesssim 25$, with the canonical Starobinsky model ($α= 1$) predicting $n_s = 0.958-0.963$ for reheating temperatures between $100 - 10^{10}$ GeV, in good agreement with Planck 2018 data and within the 95% CL region determined by the Planck-ACT-SPT combination, but below the 95% confidence region of the Planck-ACT-DESI combination. Higher reheating temperatures from near-instantaneous reheating improve the compatibility. T-models predict slightly lower $n_s$ values (0.956-0.961), in some tension with Planck 2018 data, and we find an upper limit of $α\lesssim 11$ in these models. We extend our analysis to generalized $α$-attractors with monomial potentials $V(φ) \propto φ^k$ near the minimum, demonstrating that models with $k \geq 6$ naturally predict $n_s \simeq 0.965 - 0.968$ for typical number of $e$-folds, in better agreement with the ACT DR6 data. We also consider deformed E- and T-models, which allow significantly higher values of $n_s$ for low values of $α\simeq 1$.
title Constraints on Attractor Models of Inflation and Reheating from Planck, BICEP/Keck, ACT DR6, and SPT-3G Data
topic High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2510.18656