The Effective Field Theory Approach to the Strong Coupling Issue in F(t) Gravity
Journal of Cosmology and Astroparticle Physics(2023)
摘要
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.
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关键词
Cosmological perturbation theory in GR and beyond,modified gravity
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