Evidence for suppression of structure growth in the concordance cosmological model

Understand

We present evidence for a suppressed growth rate of large-scale structure during the dark-energy dominated era.

• Modeling the growth rate of perturbations with the ``growth index'' $\gamma$, we find that current cosmological data strongly prefer a higher growth index than the value $\gamma=0.55$ predicted by general relativity in a flat $\Lambda$CDM cosmology.
• Both the cosmic microwave background data from Planck and the large-scale structure data from weak lensing, galaxy clustering, and cosmic velocities separately favor growth suppression.
• When combined, they yield $\gamma=0.633^{+0.025}_{-0.024}$, excluding $\gamma=0.55$ at a statistical significance of 3.7$\sigma$.