Hole Superconductivity in MgB_2, Cuprates, and Other Materials
The theory of hole superconductivity proposes that MgB_2, and the high Tc cuprates, and the 'conventional superconductors', and all other superconductors, are driven by the same physical mechanism, which is not the electron-phonon interaction. That mechanism, hole undressing, evidence supporting it, and predictions for MgB_2, are briefly reviewed.