2020/09/30 by Béatrice Bonga, Kartik Prabhu · 36 citations
Mathematics · Physics and Astronomy · #Astronomy #Black Holes and Theoretical Physics #Cosmology #Cosmology and Gravitation Theories #Geometry #Homogeneous space #Mathematics #Noncommutative and Quantum Gravity Theories #Physics #Theoretical physics #gr-qc #hep-th #math-ph #math.MP
paper · pdf · doi:10.1103/physrevd.102.104043
published in Physical review. D/Physical review. D. 102(10) (American Physical Society) · v2: added appendix on spatially open case; typos corrected and references updated (accepted in PRD) v1: 32 pages + one appendix + one figure (in this article we also review the notion of asymptotically flat spacetimes)
arxiv created 2020/11/11 · openalex publication_date 2020/11/16 · arxiv updated 2020/11/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Null infinity in asymptotically flat spacetimes posses a rich mathematical structure; including the Bondi-Metzner-Sachs (BMS) group and the Bondi news tensor that allow one to study gravitational radiation rigorously. However, Friedmann-Lema\\itre-Robertson-Walker (FLRW) spacetimes are not asymptotically flat because their stress-energy tensor does not decay sufficiently fast, and, in fact diverges, at null infinity. This class includes matter- and radiation-dominated FLRW spacetimes. We define a class of spacetimes whose structure at null infinity is similar to FLRW spacetimes: the stress-energy tensor is allowed to diverge and the conformal factor is not smooth at null infinity. Interestingly, for this larger class of spacetimes, the asymptotic symmetry algebra is similar to the BMS algebra but not isomorphic to it. In particular, the symmetry algebra is the semidirect sum of supertranslations and the Lorentz algebra, but it does not have any preferred translation subalgebra. Future applications include studying gravitational radiation in FLRW, the full nonlinear theory, including the cosmological memory effect, and also asymptotic charges in this framework.