| dc.description.abstract | Cosmology as the study of the Universe as a whole, addresses questions on its origin and
development and among the fundamental problems in cosmology today is the formation
and evolution of structures in the Universe. One of the proposed successful cosmological
models tested experimentally in addressing this problem is the Friedmann model based on
the cosmological principle. This thesis explores the fundamental cosmological principle,
with a specific focus on the homogeneity and isotropy assumptions inherent in the
Friedmann model underpinning the standard model. The cosmological principle says that
the Universe is isotropic and homogeneous on large scales. However, current three
dimensional redshift surveys that map the Universe depict inhomogeneities at all scales
contrary to the cosmological principle view that cosmic matter distribution is statistically
isotropic and homogeneous at large length scales. Additionally, there has been an ongoing
cosmological debate on whether or not the analyses showing fractal clustering is carried
using proper treatment of data, most notably a reliable and accurate amount of available
statistical data. These galaxy surveys provide limited statistical data depended on our
ability to measure distance accurately. The uncertainties associated with cosmic distance
measures are huge and unresolved to date while the availability of huge observational data
will wait for the next generation of bigger and advanced telescopes. To address this
challenge, the research proposed a modified Friedmann model describing relativistic
dynamics, structure formation and evolution based on the distribution of luminous matter
in the Universe. In the modified model in which the redshift scale factor relation has been
modified, it was assumed that there is huge and accurate astronomical data for measured
redshift, number density of galaxies counts per solid angle in a given direction and light
intensity counts . Interconnections between these three astronomical quantities was found
using Einstein Field Equations. Computer simulations of the derived analytical results
produced and obtained results related to structure formation in a matter―dominated
modified Friedmann Universe without dark energy. Galaxy formation, evolution and
distribution explained with a modified redshift formalism and compared to the standard
model predictions. Analysis of the results suggests that the model can account for cosmic
acceleration expansion without the need for dark energy. Simulations based on these
models have illuminated structure formation and evolution processes of the early Universe
running into the future. The simulations and analytical solutions reveal a unique pattern
in the formation and evolution of cosmic structures, particularly in galaxy formation. This
pattern shows a significant burst of activity between redshifts 0 < z < 0.4, which then
progresses rapidly until approximately z ≈ 0.9, indicating that majority of cosmic
structures formed during this period. Subsequently, the process slows down considerably,
reaching a nearly constant rate until around z ≈ 1.6, after which a gradual decline begins.
There is a distinctive redshift transition around z ≈ 0.9 is observed before the onset of
dark―matter―induced accelerated expansion. This transition is proportional to mass
matter density and geometry of the Universe. The model’s ability to explain cosmic
acceleration without requiring fine-tuning of the cosmological constant highlights its
novelty, providing a fresh perspective on the dynamic evolution of the universe. | en_US |
