Evolution of Entropy with Cosmic Time

TL;DR

This paper explores how entropy evolves in a flat universe, analyzing contributions from matter, radiation, and dark energy, and highlighting the transition from radiation to matter dominance over cosmic time.

Contribution

It provides a theoretical framework for understanding entropy evolution in a flat universe, emphasizing the roles of different components and their scaling relations.

Findings

Radiation entropy dominates early universe

Matter entropy becomes dominant as universe expands

Dark energy entropy remains constant over time

Abstract

Understanding the evolution of entropy in the universe is a fundamental aspect of cosmology. This paper investigates the evolution of entropy in a spatially flat $K=0$ universe, focusing on the contributions of matter, radiation, and dark energy components. The study derives the rate of change of entropy with respect to cosmic time, taking into account the scaling relations of energy densities and temperatures for different components. The analysis reveals the dominance of radiation entropy at early times, transitioning to matter dominance as the universe expands. The constant contribution of dark energy entropy throughout cosmic time is also considered. The paper acknowledges the limitations of the simplified model and the omission of entropy generation processes, emphasizing the importance of future research to incorporate these aspects. The results highlight the complex interplay between different components and provide insights into the dynamics of entropy in the expanding universe. This study lays the foundation for further investigations into entropy evolution, urging the consideration of more comprehensive models and numerical techniques to achieve a deeper understanding of the universe's thermodynamic behavior.