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arXiv · 2509.04105

Beyond the Starobinsky model after ACT

Min Gi Park·Dhong Yeon Cheong·Seong Chan Park
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Abstract

We revisit higher order corrections to the Starobinsky inflationary model using the most recent P-ACT-LB-BK18 data, which exhibits a mild but definite tension with the predictions of the original model. Our results demonstrate how even small {higher order} deformations of the Ricci scalar (e.g. $R^3, R^4,\cdots$) can bring the model into better agreement with current data and impose nontrivial constraints on the post-inflationary dynamics.

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Min Gi Park, Dhong Yeon Cheong, Seong Chan Park. 2025-09-04. Beyond the Starobinsky model after ACT. https://doi.org/10.1016/j.physletb.2026.140217

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