Observational constraints on the non-flat $$\Lambda CDM$$ model and a null test using the transition redshift

Abstract

A natural extension of the standard cosmological model are models that include curvature as a free parameter. In this work we study in detail the observational constraints on the non-flat C DM model using the two main geometric tests: SNIa and Hubble parameter measurements. In general we show that the observational constraints on the parameters of the C DM model strongly depend on the curvature parameter. In particular, we study the constraints on the transition redshift (z t ) of a universe dominated by matter for a universe dominated by the cosmological constant. Using this observable we construct a new null test defining ζ = z t, f lat − z t,non f lat . This test depends only on the data of the Hubble parameter, the Hubble constant and the matter density parameter. However, it does not depend on derivative of an observable as generally many tests in the literature. To reconstruct this test, we use the Gaussian process method. When we use the best-fit parameters values of P L ANC K /2018, we find no evidence of a disagreement between the data and the standard model (flat C DM), but if we use the value H 0 from R I E SS/2018 we found a disagreement with respect at the standard model. However, it is important to note that the Hubble parameter data has large errors for a solid statistical analysis.

The growth factor parametrization versus numerical solutions in flat and non-flat dark energy models

“…For example, the H 0 tension: local measurements of the Hubble parameter have a tension of at least 4σ with measurements of H 0 using data from the Planck Collaboration [9]. Also, some researchers have determined a certain curvature tension [30], this is, many observational data are statistically better fit for closed curvature models, including Planck lensing data [31][32][33][34][35][36][37][38][39][40][41][42][43][44]. In the present work we are interested in investigating the implications of introducing curvature in the study of linear growth factor.…”

Constraints from observational data for a running cosmological constant and warm dark matter with curvature

“…In our case, the theoretical power spectrum, (P the ), results from the solution of the coupled system of Eqs. ( 39), ( 40) and ( 42)- (44). Namely, the power spectrum of the normal (baryonic) matter at the current redshift is determined as…”

The growth factor parametrization versus numerical solutions in flat and non-flat dark energy models

“…For example, the H 0 tension: local measurements of the Hubble parameter have a tension of at least 4σ with measurements of H 0 using data from the Planck Collaboration [9]. Also, some researchers have determined a certain curvature tension [30], this is, many observational data are statistically better fit for closed curvature models, including Planck lensing data [31]- [44]. In the present work we are interested in investigating the implications of introducing curvature in the study of linear growth factor.…”