Ab initio Green's function theory of polarons

State-of-the-art ab initio approaches to study polarons fall into two main categories: many-body perturbation theory methods and adiabatic DFT calculations. In this talk, we present a general Green's function theory of self-trapped polarons which unifies these two seemingly disconnected approaches. We outline a series of approximations that make our theory readily amenable for implementation in current codes, and provide benchmark calculations within the Fröhlich model. This work opens the way towards full many-body calculations of polarons in real materials.