The Entropy of the Microwave Background and the Acceleration of the Universe

TL;DR

This paper discusses how the entropy of the microwave background is limited by the universe's acceleration due to a cosmological constant, contrasting it with the much larger entropy of de Sitter space.

Contribution

It provides a theoretical bound on microwave background entropy in an accelerating universe with a cosmological constant.

Findings

Microwave background entropy is bounded by ^{-3/4} ^{91}

Observed microwave background entropy is approximately 10^{85}

Entropy bounds are due to limited local degrees of freedom

Abstract

If the present acceleration of the universe is due to a cosmological constant, \lambda, then the entropy of the microwave background is bounded. It cannot exceed \lambda^{-3/4} \sim 10^{91}, which is much less than the entropy of empty de Sitter space \lambda^{-1} \sim 10^{122}. This is due to the limited efficiency of storing entropy by local field theoretical degrees of freedom. The observed entropy of the microwave background is of O(10^{85}).