Entropy of Microwave Background Radiation in Observable Universe

TL;DR

This paper derives a bound on the entropy of microwave background radiation in the observable universe based on the cosmological constant, explaining why the current entropy value is as observed.

Contribution

It introduces a new bound on microwave background entropy related to the cosmological constant, independent of reheating details.

Findings

Entropy bound: S ≤ S_{Λ_0}^{3/4}

Bound is independent of reheating energy scale

Explains the current observed entropy value

Abstract

We show that the cosmological constant at late time places a bound on the entropy of microwave background radiation deposited in the future event horizon of a given observer, $S\leq S_{\Lambda_0}^{3/4}$. This bound is independent of the energy scale of reheating and the FRW evolution after reheating. We also discuss why the entropy of microwave background in our observable universe has its present value.