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Universe 2016, 2(4), 23;

General Relativity and Cosmology: Unsolved Questions and Future Directions

1,†,* and 1,2,3,†
Paris Centre for Cosmological Physics, APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/lrfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, 75205 Paris CEDEX 13, France
Physics Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, 94720 CA, USA
Helmut and Anna Pao Sohmen Professor-at-Large, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077 Hong Kong, China
Author to whom correspondence should be addressed.
Academic Editors: Lorenzo Iorio and Elias C. Vagenas
Received: 21 August 2016 / Revised: 13 September 2016 / Accepted: 14 September 2016 / Published: 28 September 2016
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For the last 100 years, General Relativity (GR) has taken over the gravitational theory mantle held by Newtonian Gravity for the previous 200 years. This article reviews the status of GR in terms of its self-consistency, completeness, and the evidence provided by observations, which have allowed GR to remain the champion of gravitational theories against several other classes of competing theories. We pay particular attention to the role of GR and gravity in cosmology, one of the areas in which one gravity dominates and new phenomena and effects challenge the orthodoxy. We also review other areas where there are likely conflicts pointing to the need to replace or revise GR to represent correctly observations and consistent theoretical framework. Observations have long been key both to the theoretical liveliness and viability of GR. We conclude with a discussion of the likely developments over the next 100 years. View Full-Text
Keywords: General Relativity; gravitation; cosmology; Concordance Model; dark energy; dark matter; inflation; large-scale structure General Relativity; gravitation; cosmology; Concordance Model; dark energy; dark matter; inflation; large-scale structure

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Debono, I.; Smoot, G.F. General Relativity and Cosmology: Unsolved Questions and Future Directions. Universe 2016, 2, 23.

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