Angular momentum at null infinity in higher dimensions
  We define the angular momentum at null infinity in higher dimensions. The asymptotic symmetry at null infinity becomes the Poincare group in higher dimensions. This fact implies that the angular momentum can be defined without any ambiguities such as supertranslation in four dimensions. Indeed we can show that the angular momentum in our definition is transformed covariantly with respect to the Poincare group. 
Kentaro Tanabe, Tetsuya Shiromizu, Shunichiro Kinoshita
gr-qc hep-th