An Investigation on Whether or not our Universe is Friedmannian on Large Scales

Abstract

According to the cosmological model that has been widely accepted for a long time, our universe at large is well described by a Friedmann model in which the universe has been expanding from a short time after a very hot, almost point-like "big bang". The Friedmann universe embodies the cosmological principle according to which our universe, at large scales, should look homogeneous and isotropic. Nevertheless, as galaxy redshift surveys based on distance measurements probe deeper into the universe, they uncover larger and larger structures, such as sheets, clusters and superclusters, walls and voids that give evidence of inhomogeneity at all scales, hence point to a fractal universe. This raises the question as to whether, at some scale, our universe can indeed be modeled by the Friedmann universe. This question together with the Einstein's equations of dynamics and evolution of the universe based on the Friedmann metric are introduced in chapter 1. In chapter 2, the problem posed by catalogues that involve distance measurements and hence point to fractality has been made much clearer by discussing various methods used to obtain these distances. Misinterpretations of observational data obtained through such distance measurements is also discussed. In chapter 3, a method that does not rely on distance measurements but on redshift, light intensity and number density of galaxies has been clearly explained and the relevant Einstein's equations derived. The analytic and graphical evaluation of the results (computer simulations) for the functional interdependence of the above astronomical quantities are obtained in chapter 4. Finally, the work is concluded and recommendations made in chapter 5.