The entropy of the microwave background and the acceleration of the universe

Abstract

If the present acceleration of the universe is due to a cosmological constant, λ, then the entropy of the microwave background is bounded. It cannot exceed λ-3/4 ∼ 1091, which is much less than the entropy of empty de Sitter space λ-1 ∼ 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(1085). © SISSA/ISAS 2003.