Crisis in Cosmology : Observational Constraints on Omega and H_0

TL;DR

This paper reviews current observational and theoretical constraints in cosmology, highlighting the limited parameter space for flat Friedmann models despite the inclusion of a cosmological constant, based on diverse astrophysical data.

Contribution

It provides a comprehensive assessment of observational constraints on cosmological parameters, emphasizing the tight limits on models with a cosmological constant.

Findings

Small allowed parameter space for flat Friedmann models with cosmological constant

Constraints from globular cluster ages and Hubble's constant

Limits from galaxy cluster abundance and high redshift objects

Abstract

Thanks to new technology of observations and fresh inputs from particle physics, cosmology has advanced on both observational and theoretical fronts. It is therefore opportune that we take stock of the cosmological situation today and examine the observational and theoretical constraints as they are now. The bottom line in this review is that despite the availability of the cosmological constant as an extra parameter for flat Friedmann models, the allowed parameter space for such models is very small. The observations that we consider here include the ages of globular clusters, measurement of Hubble's constant, abundance of rich clusters of galaxies, fraction of mass contributed by baryons in rich clusters and abundance of high redshift objects.