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A modified form of non-locally corrected theory of gravity is investigated in the context of cosmology and the Newtonian limit. This form of non-local correction to classic Einstein-Hilbert action can be locally represented by a…

General Relativity and Quantum Cosmology · Physics 2015-05-30 Dao-Jun Liu , Bin Yang , Xing-Hua Jin

Inspired by some recent works of Lovelock Brans-Dicke gravity and mimetic gravity, cosmology solutions in extensions of these two modified gravities are investigated. A non-local term is added to the Lovelock Brans-Dicke action and…

General Relativity and Quantum Cosmology · Physics 2016-12-14 Yi Zhong , Emilio Elizalde

We investigate the gravitational backreaction, generated by coupling a general conformal sector to external, classical gravity, as described by a conformal anomaly effective action. We address the issues raised by the regularization of the…

High Energy Physics - Theory · Physics 2022-12-28 Claudio Corianò , Matteo Maria Maglio , Dimosthenis Theofilopoulos

A nonlocal version of Einstein-Gauss Bonnet (EGB) gravity can be generated by a procedure that follows closely the steps of the derivation of the conformal anomaly effective action. The action is obtained using a Weyl decomposition of the…

High Energy Physics - Theory · Physics 2023-06-01 Claudio Corianò , Mario Cretì , Stefano Lionetti , Matteo Maria Maglio , Riccardo Tommasi

We consider the most general quadratic in curvature stringy motivated non-local action for the modified Einstein's gravity. We present exact analytic cosmological solutions including the bouncing ones and develop the relevant techniques for…

Cosmology and Nongalactic Astrophysics · Physics 2013-12-03 Alexey S. Koshelev

We discuss the cosmological reconstruction in modified Gauss-Bonnet and F(R) gravities. Two alternative representations of the action (with and without auxiliary scalar) are considered. The approximate description of…

High Energy Physics - Theory · Physics 2014-11-20 Shin'ichi Nojiri , Sergei D. Odintsov , Alexey Toporensky , Petr Tretyakov

This paper is devoted to investigate the recently proposed modified Gauss-Bonnet $f(\mathcal{G},T)$ gravity, with $\mathcal{G}$, the Gauss-Bonnet term, coupled with ${T}$, the trace of energy-momentum tensor. We have used the Noether…

General Relativity and Quantum Cosmology · Physics 2017-07-12 M. Farasat Shamir , Mushtaq Ahmad

This paper is devoted to a simple nonlocal de Sitter gravity model and its exact vacuum cosmological solutions. In the Einstein-Hilbert action with $\Lambda$ term, we introduce nonlocality by the following way: $R - 2 \Lambda =…

General Relativity and Quantum Cosmology · Physics 2022-12-28 Ivan Dimitrijevic , Branko Dragovich , Zoran Rakic , Jelena Stankovic

We investigate the different energy conditions in nonlocal gravity, which is obtained by adding an arbitrary function of d'Alembertian operator, $f(\Box^{-1})$, to the Hilbert- Einstein action. We analyze the validity of four different…

General Relativity and Quantum Cosmology · Physics 2019-10-15 M. Ilyas

Towards the investigation of the full dynamics in higher-dimensional and/or stringy gravitational model, we present the basic equations of the Einstein-Gauss-Bonnet gravity theory. We show $(N+1)$-dimensional version of the ADM…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Takashi Torii , Hisa-aki Shinkai

Non-local gravity cosmologies are considered under the standard of Noether Symmetry Approach. In particular, we focus on non-local theories whose gravitational actions depend on curvature and Gauss-Bonnet scalar invariants. Specific…

General Relativity and Quantum Cosmology · Physics 2020-12-03 Francesco Bajardi , Salvatore Capozziello , Daniele Vernieri

A non-local gravity model, which includes a function $f(\Box^{-1} R)$, where $\Box$ is the d'Alembert operator, is considered. For the model with an exponential $f(\Box^{-1} R)$ de Sitter solutions are explored, without any restrictions on…

General Relativity and Quantum Cosmology · Physics 2019-10-30 E. Elizalde , E. O. Pozdeeva , S. Yu. Vernov

We investigate the scalar field dynamics of models with nonminimally coupled scalar fields in the presence of the Gauss-Bonnet term and derive the structure of the effective potential and conditions for stable de Sitter solutions in…

General Relativity and Quantum Cosmology · Physics 2019-10-21 Ekaterina O. Pozdeeva , Mohammad Sami , Alexey V. Toporensky , Sergey Yu. Vernov

We consider a modification of GR with a special type of a non-local f(R). The structure of the non-local operators is motivated by the string field theory and p-adic string theory. The spectrum is derived explicitly and the ghost-free…

High Energy Physics - Theory · Physics 2019-08-05 I. Dimitrijevic , B. Dragovich , A. S. Koshelev , Z. Rakic , J. Stankovic

We consider some cosmological aspects of nonlocal modified gravity with $\Lambda$ term, where nonlocality is of the type $R \mathcal{F}(\Box) R$. Using ansatz of the form $\Box R = r R +s,$ we find a few a(t) nonsingular bounce cosmological…

General Relativity and Quantum Cosmology · Physics 2015-08-20 I. Dimitrijevic , B. Dragovich , J. Grujic , Z. Rakic

Considering both the Gauss-Bonnet and the Born-Infeld terms, which are on similar footing with regard to string corrections on the gravity side and electrodynamic side, we present a new class of rotating solutions in Gauss-Bonnet gravity…

High Energy Physics - Theory · Physics 2008-11-26 M. H. Dehghani , S. H. Hendi

Motivated by the dark energy issue, a minisuperspace approach to the stability for modified gravitational models in a four dimensional cosmological setting are investigated. Specifically, after revisiting the $f(R)$ case, $R$ being the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Guido Cognola , Monica Gastaldi , Sergio Zerbini

We consider dark energy cosmology in a de Sitter universe filled with quantum conformal matter. Our model represents a Gauss-Bonnet model of gravity with contributions from quantum effects. To the General Relativity action an arbitrary…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Iver Brevik , John Quiroga Hurtado

We study dynamics of induced gravity cosmological models with the sixth degree polynomial potentials, that have been constructed using the superpotential method. We find conditions on the potential under which exact bounce solutions exist…

General Relativity and Quantum Cosmology · Physics 2018-10-22 E. O. Pozdeeva , S. Yu. Vernov

I review a class of nonlocally modified gravity models which were proposed to explain the current phase of cosmic acceleration without dark energy. Among the topics considered are deriving causal and conserved field equations, adjusting the…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-18 R. P. Woodard