https://doi.org/10.1140/epjc/s10052-024-12953-w
Regular Article – Theoretical Physics
Reconstructing the growth index 
with Gaussian processes
1
Observatório Nacional, Rua General José Cristino 77, São Cristóvão, 20921-400, Rio de Janeiro, RJ, Brazil
2
Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil
3
Divisão de Astrofísica, Instituto Nacional de Pesquisas Espaciais, Avenida dos Astronautas 1758, São José dos Campos, 12227-010, São Paulo, Brazil
Received:
23
November
2023
Accepted:
26
May
2024
Published online:
25
June
2024
Alternative cosmological models have been proposed to alleviate the tensions reported in the concordance cosmological model, or to explain the current accelerated phase of the universe. One way to distinguish between General Relativity and modified gravity models is using current astronomical data to measure the growth index , a parameter related to the growth of matter perturbations, which behaves differently in different metric theories. We propose a model independent methodology for determining , where our analyses combine diverse cosmological data sets, namely 
, 
, and 
, and use Gaussian Processes, a non-parametric approach suitable to reconstruct functions. This methodology is a new consistency test for constant. Our results show that, for the redshift interval 
, is consistent with the constant value 
, expected in General Relativity theory, within 
confidence level (CL). Moreover, we find 
= 0.311 
and 
for the reconstructions using the and data sets, respectively, values that also agree at a 2
CL with . Our methodology and analyses can be considered as an alternative approach in light of the current discussion in the literature that suggests a possible evidence for the growth index evolution.
© The Author(s) 2024
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