Linear growth in power law $f(T)$ gravity

Understand

We provide for the first time the growth index of linear matter fluctuations of the power law $f(T) \propto (-T)^{b}$ gravity model.

• We find that the asymptotic form of this particular $f(T)$ model is $\gamma \approx \frac{6}{11-6b}$ which obviously extends that of the $\Lambda$CDM model, $\gamma_{\Lambda}\approx 6/11$.
• Finally, we generalize the growth index analysis of $f(T)$ gravity in the case where $\gamma$ is allowed to vary with redshift.