Hamiltonian description of radiation phenomena: Trautman-Bondi energy   and corner conditions
  Cauchy initial value problem on a hyperboloid is proved to define a Hamiltonian system, provided the radiation data at null infinity are also taken into account, as a part of Cauchy data. The "Trautman-Bondi mass", supplemented by the "already radiated energy" assigned to radiation data, plays role of the Hamiltonian function. This approach leads to correct description of the corner conditions. 
Witold Chmielowiec, Jerzy Kijowski