Testing General Relativity with Present and Future Astrophysical Observations

Emanuele Berti, Enrico Barausse, Vitor Cardoso, Leonardo Gualtieri, Paolo Pani, Ulrich Sperhake, Leo C. Stein, Norbert Wex, Kent Yagi, Tessa Baker, C. P. Burgess, Flávio S. Coelho, Daniela Doneva, Antonio De Felice, Pedro G. Ferreira, Paulo C. C. Freire, James Healy, Carlos Herdeiro, Michael Horbatsch, Burkhard Kleihaus, Antoine Klein, Kostas Kokkotas, Jutta Kunz, Pablo Laguna, Ryan N. Lang, Tjonnie G. F. Li, Tyson Littenberg, Andrew Matas, Saeed Mirshekari, Hirotada Okawa, Eugen Radu, Richard O'Shaughnessy, Bangalore S. Sathyaprakash, Chris Van Den Broeck, Hans A. Winther, Helvi Witek, Mir Emad Aghili, Justin Alsing, Brett Bolen, Luca Bombelli, Sarah Caudill, Liang Chen, Juan Carlos Degollado, Ryuichi Fujita, Caixia Gao, Davide Gerosa, Saeed Kamali, Hector O. Silva, João G. Rosa, Laleh Sadeghian, Marco Sampaio, Hajime Sotani, Miguel Zilhao

Published 2015-01-28Version 1

One century after its formulation, Einstein's general relativity has made remarkable predictions and turned out to be compatible with all experimental tests. Most (if not all) of these tests probe the theory in the weak-field regime, and there are theoretical and experimental reasons to believe that general relativity should be modified when gravitational fields are strong and spacetime curvature is large. The best astrophysical laboratories to probe strong-field gravity are black holes and neutron stars, whether isolated or in binary systems. We review the motivations to consider extensions of general relativity. We present a (necessarily incomplete) catalog of modified theories of gravity for which strong-field predictions have been computed and contrasted to Einstein's theory, and we summarize our current understanding of the structure and dynamics of compact objects in these theories. We discuss current bounds on modified gravity from binary pulsar and cosmological observations, and we highlight the potential of future gravitational wave measurements to inform us on the behavior of gravity in the strong-field regime.