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

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...

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Published inJournal of cosmology and astroparticle physics Vol. 2023; no. 7; pp. 60 - 77
Main Authors Hu, Yu-Min, Zhao, Yaqi, Ren, Xin, Wang, Bo, Saridakis, Emmanuel N., Cai, Yi-Fu
Format Journal Article
LanguageEnglish
Published Bristol IOP Publishing 01.07.2023
Subjects
Cosmological perturbation theory in GR and beyond
Coupling
Field theory
modified gravity
Perturbation
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Summary: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. We find that no new scalar mode is present in both 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.
ISSN:1475-7516
1475-7516
DOI:10.1088/1475-7516/2023/07/060