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arXiv · 2609.22933

Modified Gravity Framework for the Woods-Saxon Inflation: Theoretical Foundations and Observational Constraints

Feyzollah Younesizadeh·Davoud Kamani·Younes Younesizadeh
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Abstract

We investigate an inflationary scenario within a modified gravity theory that extends the Einstein-Hilbert action through a non-minimal coupling between the inflaton $ϕ$ and the trace of the energy-momentum tensor $T$. This $f(ϕ)T$ framework is designed to naturally recover the standard general relativity in the post-inflationary universe. Within this theory, we apply the Woods-Saxon potential. The slow-roll dynamics yields a luminal sound speed $c_s^2=1$ for our specific choice of the coupling function. For the model parameters $a \lesssim 1$ and the modest coupling $β=0.1$, we obtain a scalar spectral index $n_s\approx0.959$--$0.966$ and a tensor-to-scalar ratio $r<0.01$, which reveal a good agreement with the latest Planck and BICEP/Keck data on the $(n_s, r)$ constraints. Crucially, we shall demonstrate that the $f(ϕ)T$ coupling is essential for the observational viability of the model with respect to the CMB two-point statistics. This work establishes a viable inflationary scenario within the scope of the inflationary observables which are considered here.

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Feyzollah Younesizadeh, Davoud Kamani, Younes Younesizadeh. 2026-09-19. Modified Gravity Framework for the Woods-Saxon Inflation: Theoretical Foundations and Observational Constraints. https://arxiv.org/abs/2609.22933

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