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Gravitation

About: Gravitation is a research topic. Over the lifetime, 29306 publications have been published within this topic receiving 821510 citations.


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TL;DR: This work investigates gravitational phenomenology in compactified higher-dimensional theories, with particular emphasis on the consequences in string theory of tensor-induced spontaneous Lorentz-symmetry breaking.
Abstract: We investigate gravitational phenomenology in compactified higher-dimensional theories, with particular emphasis on the consequences in string theory of tensor-induced spontaneous Lorentz-symmetry breaking. The role played by this mechanism in causing a gravitational version of the Higgs effect and in compactification is explored. The experimental viability of compactified theories with zero modes is considered by examining nonleading but observable gravitational effects. Additional constraints from the observed cosmological properties of the Universe are uncovered. Our investigations significantly constrain many theories involving extra dimensions in their perturbative regime. To resolve the phenomenological difficulties one must generate masses for the higher-dimensional components of the metric while leaving massless the physical spacetime components. Some possibilities for overcoming this metric-mass problem are suggested. An open issue is whether the metric-mass problem is resolved in string theory.

355 citations

Journal ArticleDOI
TL;DR: In this paper, the divergences of the gravitational action were analyzed for space-times that are asymptotically anti-de Sitter and aflat, and the relation of this method to the traditional reference space-time is discussed.

352 citations

Journal ArticleDOI
TL;DR: In this paper, the future evolution of the dark energy universe in modified gravities, including F(R) gravity, and string-inspired scalar Gauss-Bonnet and modified Gauss−Bonnet ones, and ideal fluid with an inhomogeneous equation of state (EoS), is investigated.
Abstract: We investigate the future evolution of the dark energy universe in modified gravities, including F(R) gravity, and string-inspired scalar Gauss–Bonnet and modified Gauss–Bonnet ones, and ideal fluid with an inhomogeneous equation of state (EoS). The modified Friedmann–Robertson–Walker dynamics for all of these theories may be presented in a universal form by using the effective ideal fluid with an inhomogeneous EoS without specifying its explicit form. We construct several examples of a modified gravity which produces accelerating cosmologies ending at the finite-time future singularities of all four known types by applying a reconstruction program. Some scenarios for resolving a finite-time future singularity are presented. Among these scenarios, the most natural one is related to additional modification of the gravitational action in the early universe. In addition, late-time cosmology in the non-minimal Maxwell–Einstein theory is considered. We investigate the forms of non-minimal gravitational coupling which generate finite-time future singularities and the general conditions for this coupling such that the finite-time future singularities cannot emerge. Furthermore, it is shown that the non-minimal gravitational coupling can remove the finite-time future singularities or make the singularity stronger (or weaker) in modified gravity.

350 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023745
20221,538
20211,353
20201,587
20191,566
20181,592