2025/07/24 by Mehnaz Zahoor, S. A. Khan, Zahoor, Mehnaz +3 · 8 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Consistency (knowledge bases) #Constraint (computer-aided design) #Cosmology and Gravitation Theories #Coupling (piping) #Curvature #Galaxies: Formation, Evolution, Phenomena #Quadratic equation #Scalar (mathematics) #Scalar field #Spectral index
paper · pdf · doi:10.48550/arxiv.2507.18684
published in arXiv (Cornell University) (Cornell University)
openalex publication_date 2025/07/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Recent results from the ACT collaboration indicate a higher value for the scalar spectral index, with ns = 0.9743 ± 0.0034, which sets tighter constraints on inflationary models, and these shifts are not in favor of many pre existing scenarios, including the widely studied and accepted standard Starobinsky model. In this paper, we examine the fractional power scalar potential within the framework of Einstein Gauss Bonnet (EGB) gravity, incorporating standard slow roll approximation. The EGB theory, motivated by higher dimensional models, introduces quadratic curvature corrections and a coupling between the scalar field and the Gauss Bonnet term, thereby modifying the cosmological dynamics. The results show good agreement with observational data, placing the predictions within the 1 σ region of the ACT r-ns constraint plot. Furthermore, incorporating the running of the scalar spectral index reinforces the models consistency with observational bounds. We also explore the parameter space of the EGB couplings and identify the range of free parameters for which the results of ns and r values remain within the 1 σ region of the ACT constraints. Finally, we also investigate the reheating phase, demonstrating that the model not only agrees with ACT data but also satisfies the lower bound on the reheating temperature, thereby ensuring a consistent and viable cosmological scenario.