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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: In this paper, the dynamics within virialized structures in the context of two modified gravity models, f(R) gravity and Dvali-Gabadadze-Porrati (DGP), are studied.
Abstract: Differences in masses inferred from dynamics, such as velocity dispersions or x rays, and those inferred from lensing are a generic prediction of modified gravity theories. Viable models, however, must include some nonlinear mechanism to restore general relativity (GR) in dense environments, which is necessary to pass Solar System constraints on precisely these deviations. In this paper, we study the dynamics within virialized structures in the context of two modified gravity models, f(R) gravity and Dvali-Gabadadze-Porrati (DGP). The nonlinear mechanisms to restore GR, which f(R) and DGP implement in very different ways, have a strong impact on the dynamics in bound objects; they leave distinctive signatures in the dynamical mass-lensing mass relation as a function of mass and radius. We present measurements from N-body simulations of f(R) and DGP, as well as semianalytical models that match the simulation results to surprising accuracy in both cases. The semianalytical models are useful for making the connection to observations. Our results confirm that the environment and scale dependence of the modified gravity effects have to be taken into account when confronting gravity theories with observations of dynamics in galaxies and clusters.
159 citations
TL;DR: In this paper, the effect of the presence of the ε-ensuremath{λ} term on the quasinormal behavior of higher dimensional Schwarzschild and Reissner-Nordstrom black holes was investigated.
Abstract: We find the gravitational resonance [quasinormal (QN)] modes of the higher-dimensional Schwarzschild and Reissner-Nordstr\"om black holes. The effect on the quasinormal behavior due to the presence of the $\ensuremath{\lambda}$ term is investigated. The QN spectrum is totally different for different signs of $\ensuremath{\lambda}.$ In more than four dimensions three types of gravitational modes were excited: scalar, vector, and tensor. They produce three different quasinormal spectra; thus, the isospectrality between scalar and vector perturbations, which takes place for $D=4$ Schwarzschild and Schwarzschild--de Sitter black holes, is broken in higher dimensions, that is, the scalar-type gravitational perturbations, connected with fluctuations of the black hole horizon, which damp most slowly and therefore dominate during late time of the black hole ringing.
159 citations
TL;DR: In this article, it was shown that all no-go theorems can be avoided by the light-cone approach, which results in more interaction vertices as compared to the usual covariant approach.
Abstract: We revisit the problem of interactions of higher-spin fields in flat space. We argue that all no-go theorems can be avoided by the light-cone approach, which results in more interaction vertices as compared to the usual covariant approaches. It is stressed that there exist two-derivative gravitational couplings of higher-spin fields. We show that some reincarnation of the equivalence principle still holds for higher-spin fields-the strength of gravitational interaction does not depend on spin. Moreover, it follows from the results by Metsaev that there exists a complete chiral higher-spin theory in four dimensions. We give a simple derivation of this theory and show that the four-point scattering amplitude vanishes. Also, we reconstruct the quartic vertex of the scalar field in the unitary higher-spin theory, which turns out to be perturbatively local.
159 citations
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TL;DR: Gravitational N-body simulations, that is numerical solutions of the equations of motions for N particles interacting gravitationally, are widely used tools in astrophysics, with applications from few body or solar system like systems all the way up to galactic and cosmological scales.
Abstract: Gravitational N-body simulations, that is numerical solutions of the equations of motions for N particles interacting gravitationally, are widely used tools in astrophysics, with applications from few body or solar system like systems all the way up to galactic and cosmological scales. In this article we present a summary review of the field highlighting the main methods for N-body simulations and the astrophysical context in which they are usually applied.
159 citations
TL;DR: In this article, a supersymmetric theory with vanishing energy density and cosmological constant equal to zero has been studied and shown to be stable against decay into the others, while all the rest have negative energy density.
Abstract: Globally supersymmetric theories often have several degenerate supersymmetric vacua. Gravitation splits this degeneracy in such a way that at most one of these vacuum solutions has energy density and cosmological constant equal to zero, while all the rest have negative energy density. Nevertheless, the vacuum with vanishing energy density is stable against decay into the others.
159 citations