Book•
General Relativity
01 Jan 1984-
About: The article was published on 1984-01-01 and is currently open access. It has received 8137 citations till now. The article focuses on the topics: Initial value formulation & Hole argument.
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TL;DR: A new optimization algorithm based on the law of gravity and mass interactions is introduced and the obtained results confirm the high performance of the proposed method in solving various nonlinear functions.
5,501 citations
TL;DR: In this article, the structure and cosmological properties of a number of modified theories, including traditional F (R ) and Hořava-Lifshitz F ( R ) gravity, scalar-tensor theory, string-inspired and Gauss-Bonnet theory, non-local gravity, nonminimally coupled models, and power-counting renormalizable covariant gravity are discussed.
3,513 citations
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TL;DR: Various applications of f(R) theories to cosmology and gravity — such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds are reviewed.
Abstract: Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.
3,375 citations
TL;DR: The results show that the validity of the "second law" of black hole mechanics in dynamical evolution from an initially stationary black hole to a final stationary state is equivalent to the positivity of a total Noether flux, and thus may be intimately related to the positive energy properties of the theory.
Abstract: We consider a general, classical theory of gravity in $n$ dimensions, arising from a diffeomorphism-invariant Lagrangian. In any such theory, to each vector field ${\ensuremath{\xi}}^{a}$ on spacetime one can associate a local symmetry and, hence, a Noether current ($n\ensuremath{-}1$)-form j and (for solutions to the field equations) a Noether charge ($n\ensuremath{-}2$)-form Q, both of which are locally constructed from ${\ensuremath{\xi}}^{a}$ and the fields appearing in the Lagrangian. Assuming only that the theory admits stationary black hole solutions with a bifurcate Killing horizon (with bifurcation surface $\ensuremath{\Sigma}$), and that the canonical mass and angular momentum of solutions are well defined at infinity, we show that the first law of black hole mechanics always holds for perturbations to nearby stationary black hole solutions. The quantity playing the role of black hole entropy in this formula is simply $2\ensuremath{\pi}$ times the integral over $\ensuremath{\Sigma}$ of the Noether charge ($n\ensuremath{-}2$)-form associated with the horizon Killing field. Furthermore, we show that this black hole entropy always is given by a local geometrical expression on the horizon of the black hole. We thereby obtain a natural candidate for the entropy of a dynamical black hole in a general theory of gravity. Our results show that the validity of the "second law" of black hole mechanics in dynamical evolution from an initially stationary black hole to a final stationary state is equivalent to the positivity of a total Noether flux, and thus may be intimately related to the positive energy properties of the theory. The relationship between the derivation of our formula for black hole entropy and the derivation via "Euclidean methods" also is explained.
2,538 citations
TL;DR: In this paper, the boundary stress tensor associated with a gravitating system in asymptotically anti-de Sitter space is computed, and the conformal anomalies in two and four dimensions are recovered.
Abstract: We propose a procedure for computing the boundary stress tensor associated with a gravitating system in asymptotically anti-de Sitter space. Our definition is free of ambiguities encountered by previous attempts, and correctly reproduces the masses and angular momenta of various spacetimes. Via the AdS/CFT correspondence, our classical result is interpretable as the expectation value of the stress tensor in a quantum conformal field theory. We demonstrate that the conformal anomalies in two and four dimensions are recovered. The two dimensional stress tensor transforms with a Schwarzian derivative and the expected central charge. We also find a nonzero ground state energy for global AdS5, and show that it exactly matches the Casimir energy of the dual super Yang–Mills theory on S
3×R.
2,433 citations