H-FGK formalism for black-hole solutions of N=2, d=4 and d=5 supergravity

We rewrite the Ferrara-Gibbons-Kallosh (FGK) black-hole effective action of N=2, d=4,5 supergravities coupled to vector multiplets, replacing the metric warp factor and the physical scalars with real variables that transform in the same way as the charges under duality transformations, which simplifies the equations of motion. For a given model, the form of the solution in these variables is the same for all spherically symmetric black holes, regardless of supersymmetry or extremality.
Comment: 10 pages; v2: references added, some editing of the text, results unchanged; v3: references added as in the published version