Unveiling the Dynamics of the Universe

TL;DR

This review analyzes the evolution of the Universe, focusing on dark energy and modified gravity models, their theoretical foundations, observational constraints, and implications for cosmology and astrophysics.

Contribution

It provides a comprehensive analysis of various modified gravity theories and their observational constraints, highlighting their role as alternatives to dark energy in explaining cosmic acceleration.

Findings

Modified gravity models can explain cosmic acceleration without dark energy.

Observational data severely restrict viable models across scales.

Cosmological tests help distinguish between different gravity theories.

Abstract

We explore the dynamics and evolution of the Universe at early and late times, focusing on both dark energy and extended gravity models and their astrophysical and cosmological consequences. Modified theories of gravity not only provide an alternative explanation for the recent expansion history of the universe, but they also offer a paradigm fundamentally distinct from the simplest dark energy models of cosmic acceleration. In this review, we perform a detailed theoretical and phenomenological analysis of different modified gravity models and investigate their consistency. We also consider the cosmological implications of well motivated physical models of the early universe with a particular emphasis on inflation and topological defects. Astrophysical and cosmological tests over a wide range of scales, from the solar system to the observable horizon, severely restrict the allowed models of the Universe. Here, we review several observational probes -- including gravitational lensing, galaxy clusters, cosmic microwave background temperature and polarization, supernova and baryon acoustic oscillations measurements -- and their relevance in constraining our cosmological description of the Universe.