ANGULAR-MOMENTUM AND SPACE-TIME HYPERBOLOIDS

For a classical field theory, in Minkowski space-time, the field momen tum and angular momentum are defined as an integral of the appropriate density over an asymptotically null hyperboloid. We prove that for th e electromagnetic held these quantities are well defined even for char ged sources where infrared divergences are a problem for defining the angular momentum. Moreover, it is also shown that if the angular momen tum density is integrated over a null plane, the angular momentum is n ot well defined for charged sources. (C) 1995 American Institute of Ph ysics.