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Gravitational Waves from Compact Sources in de Sitter Background

The concordance model of cosmology favours a universe with a tiny positive cosmological constant. A tiniest positive constant curvature, profoundly alters the asymptotic structure, forcing a re-look at a theory of gravitational radiation. Even for compact astrophysical sources, the intuition from Minkowski background is challenged at every step. Nevertheless, at least for candidate sources such as compact binaries, it is possible to quantify influence of the cosmological constant, as small corrections to the leading order Minkowski background results. Employing suitably chosen Fermi normal coordinates in the static patch of the de Sitter background, we compute the field due to a compact source to first order in $Λ$. For contrast, we also present the field in the Poincare patch where the leading correction is in $\sqrtΛ$. We introduce a gauge invariant quantity, {\em deviation scalar}, containing polarization information and compute it in both charts for a comparison.