caa a22 4500 445386215 CHVBK 20180317143033.0 cr unu---uuuuu 170323e20111201xx s 000 0 eng 10.1007/s10714-011-1255-x doi (NATIONALLICENCE)springer-10.1007/s10714-011-1255-x Penrose Roger Mathematical Institute, 24-29 St Giles', OX1 3LB, Oxford, UK aut On cosmological mass with positive Λ [Elektronische Daten] [Roger Penrose] For asymptotically flat space-times, a very satisfactory expression for the total mass/energy of a system defined at future null infinity was provided by Bondi and Sachs, in the early 1960s. A generalization of this to space-times that are asymptotically de Sitter now has particular relevance in view of observational evidence, from 1998 onwards, indicating the presence of a positive cosmological constant Λ. In this article, some of the issues involved in such a definition are examined, showing that a somewhat different attitude to mass/energy must be taken, from that which was appropriate for asymptotically flat space-times. Two tentative suggestions are put forward for a retarded mass/energy definition with positive Λ, one based on a conformally invariant integral expression whose advanced time-derivative gives the Bondi-Sachs definition in the asymptotically flat case and the other, on the author's 1982 approach to quasi-local energy. Such expressions could have some direct relevance to the proposal of Conformal Cyclic Cosmology, for which recent analysis of the CMB has provided some striking support. The Author(s), 2011 Cosmological constant nationallicence Energy in cosmology nationallicence Bondi-Sachs mass nationallicence Conformal cyclic cosmology nationallicence General Relativity and Gravitation Springer US; http://www.springer-ny.com 43/12(2011-12-01), 3355-3366 0001-7701 43:12<3355 2011 43 10714 https://doi.org/10.1007/s10714-011-1255-x text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10714-011-1255-x text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Penrose Roger Mathematical Institute, 24-29 St Giles', OX1 3LB, Oxford, UK aut NATIONALLICENCE 773 0- General Relativity and Gravitation Springer US; http://www.springer-ny.com 43/12(2011-12-01), 3355-3366 0001-7701 43:12<3355 2011 43 10714 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer