Bondi news in de Sitter space-time

TL;DR

This paper reformulates the de Sitter spacetime in Bondi-Sachs coordinates, derives Einstein equations with a positive cosmological constant, and introduces a new, coordinate-independent Bondi news function for de Sitter space.

Contribution

It presents the first derivation of a coordinate-independent Bondi news function in de Sitter space, extending gravitational wave analysis to cosmological backgrounds.

Findings

Derived Einstein equations in Bondi form with positive cosmological constant

Expressed de Sitter metric in Bondi gauge and null tetrad

Introduced a new, coordinate-independent Bondi news in de Sitter space

Abstract

Observations have shown that a model with a positive cosmological constant is more appropriate to describe our universe. The aim of this manuscript is to study the gravitational fields in de Sitter space-time. To achieve this goal, de Sitter metric is written in Bondi Sachs form and the Einstein equations are solved for this form of the metric in presence of $\Lambda$. On the other hand, a null tetrad is defined for the de Sitter metric and its form in Bondi gauge is obtained by using the general transformation. Then a new result for the Bondi news in de Sitter background is obtained, using the coordinate independent notion of Bondi news which was first presented by Penrose in 1963.