Minimal D=4 N=2 supergravity from D = 11: an M-theory free lunch

We present a new consistent truncation of D = 11 supergravity to D = 4 N = 2 minimal gauged supergravity, on the seven-dimensional internal Riemannian space corresponding to the most general class of D = 11 solutions with an AdS 4 factor and N = 2 supersymmetry. A truncation ansatz is proposed and its consistency checked at the level of the D = 11 Bianchi identity, bosonic equations of motion, and supersymmetry variations of the gravitino. The general class includes an N = 2 AdS 4 solution dual to the conformal, low-energy physics phase corresponding to a mass deformation of the M2-brane field theory. A consistent truncation recently constructed on this particular geometry is recovered from our formalism.