Implementing F (T ) Gravity in Boltzmann Codes: A Framework for Power Spectrum Computation

TL;DR

This paper develops a framework to incorporate F(T) gravity into Boltzmann codes like CLASS by using a second-order Taylor expansion, enabling accurate power spectrum calculations for small deviations from DM.

Contribution

It introduces a novel method to handle nonlinear F(T) gravity models in Boltzmann codes through Taylor expansion, facilitating cosmological power spectrum computations.

Findings

Taylor expansion accurately models F(T) gravity for n .05

Power spectrum computations match observational data within negligible error

Framework extends Boltzmann codes to nonlinear modified gravity models

Abstract

This work investigates the nonlinearity of the power-law model of F(T) gravity, highlighting the inability of the Boltzmann solver CLASS to handle nonlinear models. As a workaround, a second-order Taylor expansion is applied to the nonlinear field equations, under the assumption that the extra degree of freedom n, which quantifies deviations from the currently favored cosmological model (\Lambda CDM), remains sufficiently small to preserve the key properties of the \Lambda CDM model. The validity of the Taylor expansion is supported by supernova data indicating n \leq 0.05, for which the power spectrum can be accurately computed within CLASS with a negligible truncation error.