Minimal massive 3D gravity unitarity redux

A geometrical analysis of the bulk and anti-de Sitter boundary unitarity conditions of 3D 'minimal massive gravity' (MMG) (which evades the 'bulk/boundary clash' of topologically massive gravity) is used to extend and simplify previous results, showing that unitarity selects, up to equivalence, a connected region in parameter space. We also initiate the study of flat-space holography for MMG. Its relevant flat space limit is a deformation of 3D conformal gravity; the deformation is both nonlinear and non-conformal, implying a linearization instability. (paper)