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arXiv · 2108.07546

Modified gravity models for inflation: In conformity with observations

Xinyi Zhang·Che-Yu Chen·Yakefu Reyimuaji
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Abstract

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct $f(\phi)T$ term, where $\phi$ is identified as the inflaton and $T$ is the trace of the energy-momentum tensor. The framework goes to Einstein gravity naturally when the inflaton decays out. We investigate inflation dynamics in this $f(\phi)T$ gravity (not to be confused with torsion-scalar coupled theories) on a general basis and then apply it to three well-motivated inflationary models. We find that the predictions for the spectral tilt and the tensor-to-scalar ratio are sensitive to this new $f(\phi)T$ term. This $f(\phi)T$ gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.

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Xinyi Zhang, Che-Yu Chen, Yakefu Reyimuaji. 2021-08-17. Modified gravity models for inflation: In conformity with observations. https://doi.org/10.1103/physrevd.105.043514

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