Translating Solitons in Generalised Robertson-Walker Geometries

We generalise the notion of translating solitons in Generalised Robertson-Walker sapcetimes, which come equipped with a natural conformal Killing time-like vector field. We single out three one-parameter families of warping functions for which these objects exist, and we fully classify the corresponding Grim Reapers -- translation-invariant solitons -- for a large family of Riemannian fibres.