Asymptotic Limit of Null Hypersurfaces
Luca Ciambelli
TL;DR
The paper develops a Carrollian framework for null hypersurfaces in asymptotically flat spacetimes within the Bondi-Sachs gauge, showing that the Raychaudhuri constraint asymptotically reproduces the Bondi mass-loss formula as a conservation law for a Carrollian stress tensor. It introduces and analyzes the null Brown-York stress tensor on finite-distance null hypersurfaces, then demonstrates that its Carrollian boundary limit yields a Carrollian stress tensor at null infinity. A central result is the precise matching between the canonical phase space on finite-distance null hypersurfaces and the Ashtekar-Streubel phase space at null infinity, establishing a concrete link between bulk null dynamics and asymptotic flat-space holography. By working in a simplified framework with a time-independent boundary metric, the subleading equations reveal the Bondi mass-loss structure and the emergence of radiative data via the News tensor, while the holographic stress tensor encodes the Bondi mass and radiative content. Overall, the work lays a robust foundation for connecting finite-distance Carrollian physics with celestial holography and flat-space gravitation, suggesting future explorations into angular-momentum dynamics, phase-space quantization, and soft-theorem correspondences.
Abstract
We study null hypersurfaces approaching null infinity in asymptotically flat spacetimes within the Bondi-Sachs gauge. The null Raychaudhuri constraint is shown to asymptote to the Bondi mass-loss formula, interpreted as a stress tensor conservation law. This stress tensor, the null Brown-York tensor, yields a Carrollian stress tensor at null infinity from the bulk. Furthermore, we establish that the canonical phase space on finite-distance null hypersurfaces asymptotes to the Ashtekar-Streubel phase space. This connection between finite-distance null physics and null infinity unveils promising insights.
