Newtonian Perturbations on Models with Matter Creation

TL;DR

This paper investigates matter creation models that can mimic dark energy effects, analyzing their impact on cosmic perturbations and comparing them to the standard Lambda-CDM model using statistical tests.

Contribution

It introduces a Neo-Newtonian approach to study perturbations in matter creation models and compares their predictions to Lambda-CDM, showing they can be observationally similar.

Findings

CCDM can replicate Lambda-CDM perturbation dynamics under certain conditions.

Statistical analyses show CCDM as a viable alternative to dark energy.

Perturbation evolution in CCDM closely matches standard cosmology in some regimes.

Abstract

Creation of Cold Dark Matter (CCDM) can macroscopically be described by a negative pressure, and, therefore, the mechanism is capable to accelerate the Universe, without the need of an additional dark energy component. In this framework we discuss the evolution of perturbations by considering a Neo-Newtonian approach where, unlike in the standard Newtonian cosmology, the fluid pressure is taken into account even in the homogeneous and isotropic background equations (Lima, Zanchin and Brandenberger, MNRAS {\bf 291}, L1, 1997). The evolution of the density contrast is calculated in the linear approximation and compared to the one predicted by the $\Lambda$CDM model. The difference between the CCDM and $\Lambda$CDM predictions at the perturbative level is quantified by using three different statistical methods, namely: a simple $\chi^{2}$-analysis in the relevant space parameter, a Bayesian statistical inference, and, finally, a Kolmogorov-Smirnov test. We find that under certain circumstances the CCDM scenario analysed here predicts an overall dynamics (including Hubble flow and matter fluctuation field) which fully recovers that of the traditional cosmic concordance model. Our basic conclusion is that such a reduction of the dark sector provides a viable alternative description to the accelerating $\Lambda$CDM cosmology.