Exploring the Growth Index $\gamma_L$: Insights from Different CMB Dataset Combinations and Approaches

Understand

In this study we investigate the growth index $\gamma_L$, which characterizes the growth of linear matter perturbations, while analysing different cosmological datasets.

• We compare the approaches implemented by two different patches of the cosmological solver CAMB: MGCAMB and CAMB_GammaPrime_Growth.
• In our analysis we uncover a deviation of the growth index from its expected $\Lambda$CDM value of $0.55$ when utilizing the Planck dataset, both in the MGCAMB case and in the CAMB_GammaPrime_Growth case, but in opposite directions.
• This deviation is accompanied by a change in the direction of correlations with derived cosmological parameters.