Banana Split: Testing the Dark Energy Consistency with Geometry and Growth

TL;DR

This study tests the consistency of the standard dark energy model by separating geometric and growth information from multiple cosmological probes, finding overall agreement with Lambda-CDM but noting some anomalies in growth measurements.

Contribution

It introduces a novel approach of splitting dark energy parameters into geometry and growth components and applies it to diverse cosmological data sets for consistency checks.

Findings

Both geometry and growth favor Lambda-CDM with Ω_M ≈ 0.3.

Redshift-space distortions favor less growth, with w ≈ -0.8.

Constraints remain tight due to probe complementarity.

Abstract

We perform parametric tests of the consistency of the standard $w$CDM model in the framework of general relativity by carefully separating information between the geometry and growth of structure. We replace each late-universe parameter that describes the behavior of dark energy with two parameters: one describing geometrical information in cosmological probes, and the other controlling the growth of structure. We use data from all principal cosmological probes: of these, Type Ia supernovae, baryon acoustic oscillations, and the peak locations in the cosmic microwave background angular power spectrum constrain the geometry, while the redshift space distortions, weak gravitational lensing and the abundance of galaxy clusters constrain both geometry and growth. Both geometry and growth separately favor the $\Lambda$CDM cosmology with the matter density relative to critical $\Omega_M\simeq 0.3$. When the equation of state is allowed to vary separately for probes of growth and geometry, we find again a good agreement with the $\Lambda$CDM value ($w\simeq -1$), with the major exception of redshift-space distortions which favor less growth than in $\Lambda$CDM at 3-$\sigma$ confidence, favoring the equation of state $w^{\rm grow}\simeq -0.8$. The anomalous growth favored by redshift space distortions has been noted earlier, and is common to all redshift space distortion data sets, but may well be caused by systematics, or be explained by the sum of the neutrino masses higher than that expected from the simplest mass hierarchies, $m_\nu \simeq 0.45$ eV. On the whole, the constraints are tight even in the new, larger parameter space due to impressive complementarity of different cosmological probes.