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The review is devoted to consideration of possible observational consequences of modified gravity theories, suggested for explanation of the contemporary accelerated expansion of the universe. The major attention is paid to F(R)-models. It…

General Relativity and Quantum Cosmology · Physics 2019-11-11 Elena Arbuzova

The purpose of this paper is to analyze the existence of static stable Einstein universe using inhomogeneous linear perturbations in the context of $f(R,T)$ gravity ($R$ and $T$ denote the scalar curvature and trace of the stress-energy…

General Relativity and Quantum Cosmology · Physics 2020-02-19 M. Sharif , Arfa Waseem

We review (and extend) the analysis of general theories of all interactions (gravity included) where the mass scales are due to dimensional transmutation. Quantum consistency requires the presence of terms in the action with four…

High Energy Physics - Theory · Physics 2021-04-12 Alberto Salvio

Conditions for the existence and stability of de Sitter space in modified gravity are derived by considering inhomogeneous perturbations in a gauge-invariant formalism. The stability condition coincides with the corresponding condition for…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Valerio Faraoni , Shahn Nadeau

A new framework to perturbative quantum gravity is proposed following the geometry of nonholonomic distributions on (pseudo) Riemannian manifolds. There are considered such distributions and adapted connections, also completely defined by a…

General Relativity and Quantum Cosmology · Physics 2014-11-18 Sergiu I. Vacaru

We analyze the foundations of Finsler gravity theories with metric compatible connections constructed on nonholonomic tangent bundles, or (pseudo) Riemannian manifolds. There are considered "minimal" modifications of Einstein gravity…

General Physics · Physics 2013-03-18 Sergiu I. Vacaru

Emergent modified gravity presents a new set of generally covariant gravitational theories in which the space-time metric is not directly given by one of the fundamental fields. A metric compatible with the modified dynamics of gravity is…

General Relativity and Quantum Cosmology · Physics 2024-04-09 Martin Bojowald , Erick I. Duque

The presence of a non-zero cosmological term in Einstein field equations can be interpreted as the physical possibility for preferred reference frames without breaking of general covariance. This possibility is used in the process of…

General Relativity and Quantum Cosmology · Physics 2009-08-11 Clovis Jacinto de Matos

The cosmological constant and its phenomenology remain among the greatest puzzles in theoretical physics. We review how modifications of Einstein's general relativity could alleviate the different problems associated with it that result…

General Relativity and Quantum Cosmology · Physics 2022-10-14 The FADE Collaboration , Heliudson Bernardo , Benjamin Bose , Guilherme Franzmann , Steffen Hagstotz , Yutong He , Aliki Litsa , Florian Niedermann

The aim of this paper is to reconstruct and analyze the stability of some cosmological models against linear perturbations in $f(\mathcal{G},T)$ gravity ($\mathcal{G}$ and $T$ represent the Gauss-Bonnet invariant and trace of the…

General Relativity and Quantum Cosmology · Physics 2017-06-22 M. Sharif , Ayesha Ikram

A modified Newton's gravity is obtained as the weak field approximation of the Einstein's equation in Finsler space. It is found that a specified Finsler structure makes the modified Newton's gravity equivalent to the modified Newtonian…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Zhe Chang , Xin Li

We consider predictions for structure formation from modifications to general relativity in which the Einstein-Hilbert action is replaced by a general function of the Ricci scalar. We work without fixing a gauge, as well as in explicit…

Astrophysics · Physics 2010-04-06 Rachel Bean , David Bernat , Levon Pogosian , Alessandra Silvestri , Mark Trodden

In this work we study the cosmology of the general f(T) gravity theory. We express the modified Einstein equations using covariant quantities, and derive the gauge-invariant perturbation equations in covariant form. We consider a specific…

Cosmology and Nongalactic Astrophysics · Physics 2011-11-02 Baojiu Li , Thomas P. Sotiriou , John D. Barrow

Stability of the Einstein static universe versus the linear scalar, vector and tensor perturbations is investigated in the context of deformed Ho\v{r}ava-Lifshitz cosmology inspired by entropic force scenario. A general stability condition…

General Relativity and Quantum Cosmology · Physics 2017-02-14 Y. Heydarzade , M. Khodadi , F. Darabi

It is offered that $F(R)-$modified gravities can be considered as nonperturbative quantum effects arising from Einstein gravity. It is assumed that nonperturbative quantum effects gives rise to the fact that the connection becomes…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Vladimir Dzhunushaliev

It has been suggested that Einstein's theory of General Relativity can be modified to accomodate mismatches between the gravitational field and luminous matter on a wide range of scales. Covariant theories of modified gravity generically…

Astrophysics · Physics 2009-03-31 P. G Ferreira , C. Skordis , C. Zunckel

We argue that the presence of conformal anomalies in gravitational theories can lead to observable modifications to Einstein's equations via the induced anomalous effective actions, whose non-localities can overwhelm the smallness of the…

General Relativity and Quantum Cosmology · Physics 2017-06-21 Krzysztof A. Meissner , Hermann Nicolai

We consider metric-affine scenarios where a modified gravitational action is sourced by electrovacuum fields in a three dimensional space-time. Such scenarios are supported by the physics of crystalline structures with microscopic defects…

General Relativity and Quantum Cosmology · Physics 2015-08-13 Cosimo Bambi , M. Ghasemi-Nodehi , D. Rubiera-Garcia

The classical Einstein's gravity can be reformulated from the constrained U(2,2) gauge theory on the ordinary (commutative) four-dimensional spacetime. Here we consider a noncommutative manifold with a symplectic structure and construct a…

High Energy Physics - Theory · Physics 2011-02-01 Yan-Gang Miao , Zhao Xue , Shao-Jun Zhang

Versions of parameterized pseudo-Newtonian gravity theories specially designed for cosmology have been introduced in recent cosmology literature. The modifications demand a zero-pressure fluid in the context of versions of modified…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Jai-chan Hwang , Hyerim Noh , Chan-Gyung Park