Consistency of LCDM with Geometric and Dynamical Probes

TL;DR

This paper reviews the LCDM model's success in fitting recent geometric data, discusses some shortcomings with specific observations, and explores the scale-dependent evolution of matter overdensity as a dynamical probe of cosmic expansion.

Contribution

It introduces a new scale-dependent parametrization for the growth rate of perturbations applicable on large cosmological scales.

Findings

LCDM fits most geometric data well

Identifies shortcomings in fitting velocity dipole flows and halo profiles

Proposes a scale-dependent growth rate parametrization

Abstract

The LCDM cosmological model assumes the existence of a small cosmological constant in order to explain the observed accelerating cosmic expansion. Despite the dramatic improvement of the quality of cosmological data during the last decade it remains the simplest model that fits remarkably well (almost) all cosmological observations. In this talk I review the increasingly successful fits provided by LCDM on recent geometric probe data of the cosmic expansion. I also briefly discuss some emerging shortcomings of the model in attempting to fit specific classes of data (eg cosmic velocity dipole flows and cluster halo profiles). Finally, I summarize recent results on the theoretically predicted matter overdensity ($\delta_m=\frac{\delta \rho_m}{\rho_m}$) evolution (a dynamical probe of the cosmic expansion), emphasizing its scale and gauge dependence on large cosmological scales in the context of general relativity. A new scale dependent parametrization which describes accurately the growth rate of perturbations even on scales larger than 100h^{-1}Mpc is shown to be a straightforward generalization of the well known scale independent parametrization f(a)=\omms(a)^\gamma valid on smaller cosmological scales.