Scalar perturbations in f(T) gravity using the 1 +3 covariant approach
Abstract
The cosmological scalar perturbations of standard matter are investigated in the context of extended teleparallel f(T) gravity theories using the 1 +3 covariant formalism. After a review of the background gravitational field equations of f(T) gravity and the introduction of the covariant perturbation variables, the usual scalar and harmonic decomposition have been performed, and the analysis of the growth of the density contrasts in the quasistatic approximation for two noninteracting fluids scenarios, namely torsiondust and torsionradiation mixtures is presented for the generic f(T) gravity theory. Special applications to two classes of f(T) gravity toy models, namely f (T ) =μ T_{0}( T/T_{0})^{n} and f (T ) =T +μ T_{0}( T/T_{0})^{n} , have then been made within the observationally viable regions of their respective parameter spaces, and the growth of the matter density contrast for both torsiondust and torsionradiation epochs of the Universe has been examined. The exact solutions of the dust perturbations, with growing amplitudes in cosmic time, are obtained for some limiting cases of n. Similarly, the long and shortwavelength modes in the torsionradiation case are treated, with the amplitudes either oscillating or monotonically growing with time. Overall, it is noted that f(T) models contain a richer set of observationally viable structure growth scenarios that can be tested against upandcoming observational data and can accommodate currently known features of the largescale structure power spectrum in the general relativistic and Λ C D M limits.
 Publication:

European Physical Journal C
 Pub Date:
 May 2020
 DOI:
 10.1140/epjc/s1005202079613
 arXiv:
 arXiv:1907.03563
 Bibcode:
 2020EPJC...80..422S
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 Published version