Joint analysis of EDGES $21$-cm line observations with standard candles and rulers in $\Lambda$CDM and non-adiabatic gCg models

TL;DR

This study explores how a generalized Chaplygin gas model with energy transfer from dark energy to dark matter can reconcile EDGES 21-cm observations with standard cosmology, showing that negative gas parameters improve data fit.

Contribution

It introduces a decomposed gCg model with negative alpha to better fit EDGES data and combines multiple cosmological datasets to constrain deviations from Lambda-CDM.

Findings

Negative alpha improves fit to EDGES data

Small deviations from Lambda-CDM are consistent with combined data

gCg model can alleviate tension between observations and standard cosmology

Abstract

A decomposed generalised Chaplygin gas (gCg) with energy flux from dark energy to dark matter, represented by a negative value for the gas parameter $\alpha$, is shown to alleviate the tension between EDGES data and the cosmological standard model. Using EDGES data and employing a Bayesian statistical analysis, the agreement with the standard model is only marginal. However, if $\alpha$ is negative enough the gCg fits remarkably well the data, even in combination with SNe Ia datasets. On the other hand, when the CMB and BAO acoustic scales are included the preferred value for $\alpha$ is near zero, implying that a small deviation from $\Lambda$CDM is predicted.