Using dark energy to suppress power at small scales

TL;DR

This paper introduces a two-parameter dark energy model that suppresses small-scale power to address tensions between CMB and low-redshift observations, providing a better fit to data than standard models.

Contribution

The paper proposes a novel scale-dependent dark energy model that reduces small-scale power, improving consistency between CMB and low-redshift measurements.

Findings

Model slightly outperforms ΛCDM with Δχ²=2.4

Achieves σ₈=0.79 ± 0.02 consistent with cluster counts

Addresses power suppression at small scales in cosmological data

Abstract

The latest Planck results reconfirm the existence of a slight but chronic tension between the best-fit Cosmic Microwave Background (CMB) and low-redshift observables: power seems to be consistently lacking in the late universe across a range of observables (e.g.~weak lensing, cluster counts). We propose a two-parameter model for dark energy where the dark energy is sufficiently like dark matter at large scales to keep the CMB unchanged but where it does not cluster at small scales, preventing concordance collapse and erasing power. We thus exploit the generic scale-dependence of dark energy instead of the more usual time-dependence to address the tension in the data. The combination of CMB, distance and weak lensing data somewhat prefer our model to $\Lambda$CDM, at $\Delta\chi^2=2.4$. Moreover, this improved solution has $\sigma_8=0.79 \pm 0.02$, consistent with the value implied by cluster counts.