Cosmological constraints on single-field inflation models from ACT/SPT data and observations at sub-Mpc scales
Abstract
We investigate single-field inflation models that can produce large curvature perturbations at sub-Mpc scales while remaining consistent with cosmological observations across multiple regimes. We highlight the tension between generating enhanced small-scale perturbations and maintaining agreement with the scalar spectral index ns measured by ACT and SPT, which disfavors several conventional single-field inflation models. To address this issue, we propose three viable classes of inflationary potentials: bump/dip-modified, step-like, and double-inflection-point. Each can sufficiently amplify primordial perturbations while predicting ns that lie within the 2σ range of current observational bounds. In addition, we examine the primordial power spectra predicted by these models and constrain their parameter spaces using cosmological observations at different scales, including CMB, BAO, PBH, PTA, and CMB-distortion. Our results show that some of the models considered can simultaneously satisfy the ACT/SPT constraints and account for the current PTA observations, although doing so while respecting the constraints on the PBH abundance remains challenging.
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BibTeX
@misc{wang2026cosmological,
title = {{Cosmological constraints on single-field inflation models from ACT/SPT data and observations at sub-Mpc scales}},
author = {Qing-Yang Wang and Jing-Zhi Zhou and Fei-Yu Chen and Zhi-Chao Li},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37383},
eprint = {2610.37383},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37383},
}
RIS
TY - UNPB
TI - Cosmological constraints on single-field inflation models from ACT/SPT data and observations at sub-Mpc scales
AU - Qing-Yang Wang
AU - Jing-Zhi Zhou
AU - Fei-Yu Chen
AU - Zhi-Chao Li
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37383
UR - https://arxiv.org/abs/2610.37383
AB - We investigate single-field inflation models that can produce large curvature perturbations at sub-Mpc scales while remaining consistent with cosmological observations across multiple regimes. We highlight the tension between generating enhanced small-scale perturbations and maintaining agreement with the scalar spectral index n_s measured by ACT and SPT, which disfavors several conventional single-field inflation models. To address this issue, we propose three viable classes of inflationary potentials: bump/dip-modified, step-like, and double-inflection-point. Each can sufficiently amplify primordial perturbations while predicting n_s that lie within the 2σ range of current observational bounds. In addition, we examine the primordial power spectra predicted by these models and constrain their parameter spaces using cosmological observations at different scales, including CMB, BAO, PBH, PTA, and CMB-distortion. Our results show that some of the models considered can simultaneously satisfy the ACT/SPT constraints and account for the current PTA observations, although doing so while respecting the constraints on the PBH abundance remains challenging.
ER -