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arXiv · 2302.03545

The effective field theory approach to the strong coupling issue in $f(T)$ gravity

Yu-Min Hu·Yaqi Zhao·Xin Ren·Bo Wang·Emmanuel N. Saridakis·Yi-Fu Cai
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Abstract

We investigate the scalar perturbations and the possible strong coupling issues of $f(T)$ around a cosmological background, applying the effective field theory (EFT) approach. We revisit the generalized EFT framework of modified teleparallel gravity and apply it by considering both linear and second-order perturbations for $f(T)$ theory. No new scalar mode is present in linear and second-order perturbations in $f(T)$ gravity, which suggests a strong coupling problem. However, based on the ratio of cubic to quadratic Lagrangians, we provide a simple estimation of the strong coupling scale, a result which shows that the strong coupling problem can be avoided at least for some modes. In conclusion, perturbation behaviors that at first appear problematic may not inevitably lead to a strong coupling problem, as long as the relevant scale is comparable with the cutoff scale $M$ of the applicability of the theory.

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Yu-Min Hu, Yaqi Zhao, Xin Ren, Bo Wang, Emmanuel N. Saridakis, Yi-Fu Cai. 2023-02-07. The effective field theory approach to the strong coupling issue in $f(T)$ gravity. https://doi.org/10.1088/1475-7516%2F2023%2F07%2F060

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