Modified gravity models for inflation: In conformity with observations

Abstract

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct $f(\varphi )T$ term, where $\varphi$ 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 $f(\varphi )T$ 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 $f(\varphi )T$ term. This $f(\varphi )T$ gravity brings chaotic and natural inflation into better agreement with data and allows a larger tensor-to-scalar ratio in the Starobinsky model.

16 pages, 3 figures. Match the version accepted for publication in PRD

References in corpus (11)

• f(R,T) gravity
• Modified teleparallel gravity: inflation without inflaton
• Extra force in $f(R)$ modified theories of gravity
• Class of viable modified $f(R)$ gravities describing inflation and the onset of accelerated expansion
• Inflationary universe from perfect fluid and $F(R)$ gravity and its comparison with observational data
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• Inflation in $f(R,T)$ Gravity
• Dimensional Transmutation in Gravity and Cosmology
• Natural inflation with a nonminimal coupling to gravity
• Natural-Scalaron Inflation
• Modified Teleparallel Gravity induced by quantum fluctuations

Cited by in corpus (11)

• Finite-time Cosmological Singularities and the Possible Fate of the Universe
• Cosmological Inflation in f(Q, T) Gravity
• Slow-roll inflation in $f(R,T)$ gravity with a $RT$ mixing term
• Testing scale-invariant inflation against cosmological data
• Reheating constraints on modified single-field Natural Inflation models
• Tsallis holographic inflation in $f(R,T)$ gravity: CMB constraints, reheating, and swampland implications
• Inflation with antisymmetric tensor field: new candidates
• The Inflationary Quartic Hilltop Model in a Modified Gravity and Its Comparison with the Observations
• $F(\varphi )T$-Gravity and Inflationary Natural Model
• Scalar and vector modes in inflation with antisymmetric tensor field
• Slow-roll Hilltop Inflation in $f(\varphi ,T)$ gravity