Non-parametric reconstruction of growth index via Gaussian processes

Abstract

The accelerated cosmic expansion could be due to dark energy within general relativity (GR), or modified gravity. It is of interest to differentiate between them, by using both the expansion history and the growth history. In the literature, it was proposed that the growth index γ is useful to distinguish these two scenarios. In this work, we consider the non-parametric reconstruction of the growth index γ as a function of redshift z from the latest observational data as of July 2018 via Gaussian Processes. We find that f (R) theories and dark energy models within GR (especially ΛCDM) are inconsistent with the results in the moderate redshift range far beyond 3σ confidence level. A modified gravity scenario different from f (R) theories is favored. However, these results can also be due to other non-trivial possibilities, in which dark energy models within GR (especially ΛCDM) and f (R) theories might still survive. In all cases, our results suggest that new physics is required.PACS numbers: 98.80.Es, 95.36.+x, 04.50.Kd

Observational constraints on growth index with cosmography

“…in the 3 cases with the Padé cosmography. This result supports our previous work [17]. On the other hand, γ 0 ≃ 0.55 (for dark energy models in GR) is consistent with the latest observational data at 1σ C.L.…”

“…Therefore, they might be distinguished from each other by combining the observations of both the expansion and growth histories (see e.g. [8][9][10][11][12][13][14][15][16][17][99][100][101] and references therein).…”

“…So, it is of interest to obtain the growth index γ from the observational data by using a model-independent approach. In fact, recently we have made an effort in [17] to obtain a nonparametric reconstruction of the growth index γ via Gaussian processes by using the latest observational data. Although the approach of Gaussian processes is clearly model-independent, its reliability at high redshift might be questionable.…”

Model-independent Reconstruction of f(T) Gravity from Gaussian Processes

“…Such a procedure has been applied to dark energy models using various datasets in order to reconstruct the evolution of the Hubble function, of the dark energy equation-of-state (EoS) parameters, of the dimensionless comoving luminosity distance, of the dark interaction term, etc. [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80].…”

Reconstructing the fraction of baryons in the intergalactic medium with fast radio bursts via Gaussian processes

“…II A. Following [49], we use the observational Pantheon sample [61][62][63][64] data are given in terms of the corrected bolometric apparent magnitude m. The quantity D introduced in the end of Sec. II A is related to m according to (see e.g.…”