79 citations · 310 across the 37 of their papers we have counts for
37 papers
Cut-continuity of twistor angular momentum
Adam D. Helfer
Chen et al. argued recently that, in Bondi-Sachs space-times, the angular momentum at scri (null infinity) should vary continuously with the position of the cut (but not depend sen…
Angular momentum, spinors and twistors
Adam D. Helfer
Twistors appear to provide a satisfactory treatment of angular momentum for gravitationally radiating systems. The approach is manifestly Bondi-Metzner-Sachs (BMS) invariant, and t…
Center-of-mass ambiguity for Bondi-Metzner-Sachs charges
Adam D. Helfer
Dray and Streubel proposed a definition of angular momentum in general relativity based on `Bondi-Metzner-Sachs (BMS) charges'. I show here that the natural definition of center of…
Fluxes and angular momentum
Adam D. Helfer
The Ashtekar-Streubel fluxes give a proposed definition of the angular momentum emitted by an isolated gravitationally radiating system. This was based on identifying a "phase spac…
Magnetic effects in general relativity: quadrupoles, shear and memory
Adam D. Helfer
Gravitational effect of "magnetic type" -- those having a curl-like character over large spheres -- are investigated, for isolated systems. The Bondi-Sachs-Newman-Penrose formalism…
Hawking radiation, quantum fields, and tunneling
Adam D. Helfer
I consider the problem of reconciling "tunneling" approaches to black-hole radiation with the treatment by quantum field theory in curved space-time. It is not possible to do this…