Cosmological Imprint of the Second Law of Thermodynamics

TL;DR

This paper explores how the second law of thermodynamics influences the evolution of the universe, particularly the onset of dark energy dominance, by analyzing cosmological data and scale factor relationships.

Contribution

It introduces two independent methods to determine the dark energy constant from observational data and links thermodynamics to cosmic evolution.

Findings

Dark energy constant d approximately equals 1

Two methods for determining d from observations

Thermodynamics sets the timing of dark energy dominance

Abstract

We study the evolution of the universe in the presence of inflaton, matter, radiation, and holographic dark energy. The time evolution of the scale factor is obtained by solving the Friedmann equation of the universe with a good approximation. We present two independent ways which determine the value of the dark energy constant $d\sim 1$ from the observational data. The two ways are measuring the deceleration parameter and measuring a universal constant depending only on $d$. The universal constant is given by a dimensionless combination of three scale factors at the equipartition times of radiation-matter, radiation-dark energy, and matter-dark energy. We also discuss that the second law of thermodynamics determines the point of time when the dark energy dominated era begins in the universe.