DUALITY COVARIANT FORMULATION OF EXTENDED SUPERGRAVITY - CENTRAL CHARGES, BPS STATES AND BLACK-HOLE ENTROPY

In these lectures we give a geometrical formulation of N-extended supe rgravities which generalizes N = 2 special geometry of N = 2 theories. In all these theories duality symmetries are related to the notion of ''flat symplectic bundles'' and central charges may be defined as ''s ections'' over these bundles. Attractor points giving rise to ''fixed scalars'' of the horizon geometry and Bekenstein-Hawking entropy formu la for extremal black-holes are discussed in some details.