One-parameter dynamical dark-energy from the generalized Chaplygin gas

TL;DR

This paper explores a one-parameter dynamical dark energy model based on the generalized Chaplygin gas, showing it closely aligns with ΛCDM and alleviates the σ8 tension using recent cosmological data.

Contribution

It introduces a specific non-adiabatic gCg model with a varying dark energy parameter, constrained by latest observational data, and demonstrates its effectiveness in reducing cosmological tensions.

Findings

Model parameters are tightly constrained by data.

Results are consistent with ΛCDM.

Reduces σ8 tension from ~3σ to ~1σ.

Abstract

The fact that Einstein's equations connect the space-time geometry to the total matter content of the cosmic substratum, but not to individual contributions of the matter species, can be translated into a degeneracy in the cosmological dark sector. Such degeneracy makes it impossible to distinguish cases where dark energy (DE) interacts with dark matter (DM) from a dynamical non-interacting scenario using observational data based only on time or distance measurements. In this paper, based on the non-adiabatic generalized Chaplygin gas (gCg) model, we derive and study some cosmological consequences of a varying one-parameter dynamical DE parameterization, which does not allow phantom crossing. We perform a parameter selection using the most recent public available data, such as the data from Planck 2018, eBOSS DR16, Pantheon and KiDS-1000. We find that current observations provide strong constraints on the model parameters, leading to values very close to the $\Lambda$CDM cosmology, at the same time that the well-known $\sigma_8$ tension is reduced from $\sim 3\sigma$ to $\sim 1\sigma$ level.