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# Modified F(R) Hořava–Lifshitz gravity: a way to accelerating FRW cosmology

Classical and Quantum Gravity (Impact Factor: 3.56). 08/2010; 27(18):185021. DOI: 10.1088/0264-9381/27/18/185021

Source: arXiv

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**ABSTRACT:**This paper reports a study on modified holographic Ricci dark energy in modified f(R) Hořava-Lifshitz gravity with a power-law form of the scale factor a. The modified Ricci scalar in the said gravity model is denoted and, accordingly, the modified gravity has the functional form . The analytical solution for the reconstructed has been obtained and it satisfies a sufficient condition for a realistic model. The effective equation of state parameter, ωeff, has been observed to have a quintessence-like behavior. Statefinder trajectories have indicated the attainment of the ΛCDM phase of the universe for the reconstructed .Canadian Journal of Physics 02/2014; 92(3). · 0.90 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We analyze gravitational theories with quadratic curvature terms, including the case of conformally invariant Weyl gravity, motivated by the intention to find a renormalizable theory of gravity in the ultraviolet region, yet yielding general relativity at long distances. In the Hamiltonian formulation of Weyl gravity, the number of local constraints is equal to the number of unstable directions in phase space, which in principle could be sufficient for eliminating the unstable degrees of freedom in the full nonlinear theory. All the other theories of quadratic type are unstable -- a problem appearing as ghost modes in the linearized theory. We find that the full projection of the Weyl tensor onto a three-dimensional hypersurface contains an additional fully traceless component, given by a quadratic extrinsic curvature tensor. A certain inconsistency in the literature is found and resolved: when the conformal invariance of Weyl gravity is broken by a cosmological constant term, the theory becomes pathological, since a constraint required by the Hamiltonian analysis imposes the determinant of the metric of spacetime to be zero. In order to resolve this problem by restoring the conformal invariance, we introduce a new scalar field that couples to the curvature of spacetime, reminiscent of the introduction of vector fields for ensuring the gauge invariance.Physical Review D 11/2013; 89(6). · 4.69 Impact Factor -
##### Article: ASPECTS OF HOŘAVA–LIFSHITZ COSMOLOGY

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**ABSTRACT:**We review some general aspects of Hořava–Lifshitz cosmology. Formulating it in its basic version, we extract the cosmological equations and we use observational data in order to constrain the parameters of the theory. Through a phase–space analysis we extract the late-time stable solutions, and we show that bouncing and cyclic behavior can arise naturally. Concerning the effective dark energy sector we show that it can describe the phantom phase without the use of a phantom field. However, performing a detailed perturbation analysis, we see that Hořava–Lifshitz gravity in its basic version, suffers from instabilities. Therefore, suitable generalizations are required in order for this novel theory to be a candidate for the description of nature.International Journal of Modern Physics D 05/2012; 20(08). · 1.03 Impact Factor

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