Revisiting a model-independent dark energy reconstruction method

TL;DR

This paper critically revisits a model-independent dark energy reconstruction method using SNeIa and GRBs, highlighting its weaknesses, sample sensitivities, and limited predictive power, while emphasizing its minimal assumptions as a complementary approach.

Contribution

It provides new insights into the method's limitations, especially regarding observational sample quality and parameter sensitivities, and clarifies the role of GRBs in cosmological reconstructions.

Findings

GRBs are poor cosmological probes compared to SNeIa.

Results are highly sensitive to sample selection and parameter choices.

The method offers a global trend view but limited detailed predictions.

Abstract

Model independent reconstructions of dark energy have received some attention. The approach that addresses the reconstruction of the dimensionless coordinate distance and its two first derivatives using a polynomial fit in different redshift windows is well developed \cite{DalyDjorgovski1,DalyDjorgovski2,DalyDjorgovski3}. In this work we offer new insights into the problem by focusing on two types of observational probes: SNeIa and GRBs. Our results allow to highlight some of the intrinsic weaknesses of the method. One of the directions we follow is to consider updated observational samples. Our results indicate than conclusions on the main dark energy features as drawn from this method are intimately related to the features of the samples themselves (which are not quite ideal). This is particularly true of GRBs, which manifest themselves as poor performers in this context. In contrast to original works, we conclude they cannot be used for cosmological purposes, and the state of the art does not allow to regard them on the same quality basis as SNeIa. The next direction we contribute to is the question of how the adjusting of some parameters (window width, overlap, selection criteria) affect the results. We find again there is a considerable sensitivity to these features. Then, we try to establish what is the current redshift range for which one can make solid predictions on dark energy evolution. Finally, we strengthen the former view that this model is modest in the sense it provides only a picture of the global trend. But, on the other hand, we believe it offers an interesting complement to other approaches given that it works on minimal assumptions.