Selectors of the duality mapping.

We introduce the concept of *-mapping as a selection of the duality mapping. We prove that the *-mappings are more general than the support mappings and provide a simple proof of the characterisation of smoothness by the norm to weak-star continuity of the *-mappings. As a consequence, we provide a characterisation of Hilbert spaces in terms of *-mappings and show that a Banach space has the Schur property if and only if it has the Dunford-Pettis property and there exists a *-mapping that is sequentially w – w continuous at 0. This last fact leads to the existence of smooth Banach spaces on which the duality mapping is not sequentially w – w continuous at 0.