http://arxiv.org/abs/2202.01002
Natural Inflation with non-minimal coupling NMC to gravity $(\xi \phi^2)$ is investigated in the context of an extended gravity of the form $R+ \alpha R^2$. The treatment is performed in the Palatini formalism.We discuss various limitations of the model “$\alpha \gg 1$ and $\alpha \ll 1$” in light of two scenarios of inflation: a “Slow roll” and a “Constant roll”.By analyzing the observational consequences of the model, our results show a significant improvement regarding compatibility between the theoretical results of this model and the experimental ones from Planck 2018, as exemplified by the tensor-to-scalar ratio and spectral index. Furthermore, a broader range of parameter space for natural inflation is now compatible with the confidence contours of Planck results. The notable effect of both NMC and $\alpha R^2$’s contributions makes it a significant improvement. $\alpha R^2$ gravity influences scalar-tensor ratio values. In contrast, NMC has a more significant impact on the spectral index values. Contributions to this area allow more excluded intervals to be included and are compatible with observational data.
M. Alhallak and M. Aldaher
Thu, 3 Feb 22
14/56
Comments: 16 pages, 7 figures , one table