No absorption in de Sitter space

TL;DR

This paper demonstrates that de Sitter space does not absorb scalar waves, indicating it remains in thermal equilibrium with its cosmological horizon emitting and absorbing radiation at equal rates.

Contribution

It provides a detailed computation of the scalar wave absorption cross section in de Sitter space, showing the absence of absorption and confirming thermal equilibrium.

Findings

No absorption of scalar waves in de Sitter space

De Sitter space maintains thermal equilibrium with its horizon

Cosmological horizon emits and absorbs radiation at equal rates

Abstract

We study the wave equation for a minimally coupled massive scalar in D-dimensional de Sitter space. We compute the absorption cross section to investigate its cosmological horizon in the southern diamond. By analogy of the quantum mechanics, it is found that there is no absorption in de Sitter space. This means that de Sitter space is usually in thermal equilibrium, like the black hole in anti de Sitter space. It confirms that the cosmological horizon not only emits radiation but also absorbs that previously emitted by itself at the same rate, keeping the curvature radius of de Sitter space fixed.