Characterization of (asymptotically) Kerr-de Sitter-like spacetimes at null infinity

We investigate solutions (M, g) to Einstein?s vacuum field equations with positive cosmological constant ? which admit a smooth past null infinity I- la Penrose and a Killing vector field whose associated MarsSimon tensor (MST) vanishes. The main purpose of this work is to provide a characterization of these spacetimes in terms of their Cauchy data on I-. Along the way, we also study spacetimes for which the MST does not vanish. In that case there is an ambiguity in its definition which is captured by a scalar function Q. We analyze properties of the MST for different choices of Q. In doing so, we are led to a definition of asymptotically Kerrde Sitter-like spacetimes, which we also characterize in terms of their asymptotic data on I-. & copy ; 2016 IOP Publishing Ltd.