Twistors And ADM Angular Momentum

Spinorial definition of ADM angular momentum for an asymptotically Euclidean initial data surface is formulated. Two equivalent definitions are given, one in terms of twistors and another one in terms of Sen-Witten spinors whose asymptotic behaviour resembles that of Euclidean three space in spherical coordinates. As consistency check, both definitions are then applied to obtain the standard angular momentum for the Kerr metric.