Cosmological Imprints of the Second Law of Thermodynamics

We study the full history 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 without artificial ansatz. We discuss that the second law of thermodynamics dictates the accelerating expansion of the dark energy dominant phase to the universe. In addition, we show that a dimensionless combination of three scale factors at the equipartition times of matter-radiation, radiation-dark energy, and matter-dark energy provides a universal constant which depends only on the dark energy constant d.