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We analyse cosmological perturbations around a homogeneous and isotropic background for scalar-tensor, vector-tensor and bimetric theories of gravity. Building on previous results, we propose a unified view of the effective parameters of…

General Relativity and Quantum Cosmology · Physics 2018-03-28 Macarena Lagos , Emilio Bellini , Johannes Noller , Pedro G. Ferreira , Tessa Baker

Dynamical systems methods are used to investigate global behavior of the spatially flat Friedmann-Robertson-Walker cosmological model in gravitational theory with a non-minimally coupled scalar field and a constant potential function. We…

General Relativity and Quantum Cosmology · Physics 2015-11-11 Orest Hrycyna , Marek Szydlowski

In this paper, a general FRW cosmological model has been constructed in $f(R,T)$ gravity reconstruction with variable cosmological constant. A number of solutions to the field equations has been generated by utilizing a form for the Hubble…

General Relativity and Quantum Cosmology · Physics 2018-10-17 Nasr Ahmed , Sultan Z. Alamri

The work shows that the associated Einstein like gravity for the Klein-Gordon field shows the spontaneous emergence of the cosmological pressure tensor density (CPTD) that in the classical limit leads to the cosmological constant (CC). Even…

General Physics · Physics 2020-07-07 Piero Chiarelli

We generalize the well-known Bonnor-Melvin solution of the Einstein-Maxwell equations to the case of a non-vanishing cosmological constant. The spacetime is again cylindrically symmetric and static but, unlike the original solution, it…

General Relativity and Quantum Cosmology · Physics 2019-03-21 Martin Zofka

We discuss the linearization of Einstein equations in the presence of a cosmological constant, by expanding the solution for the metric around a flat Minkowski space-time. We demonstrate that one can find consistent solutions to the…

General Relativity and Quantum Cosmology · Physics 2010-04-14 Jose Bernabeu , Catalina Espinoza , Nick E. Mavromatos

In this paper we construct a new kind of solutions of the Einstein's field equations with non-vanishing cosmological constant, which possess some interesting physical properties. The singularities of this kind of solutions are investigated.…

Mathematical Physics · Physics 2011-08-16 De-Xing Kong , Kefeng Liu , Ming Shen

In hep-th/0506040 we discussed a classically constrained model of gravity. This theory contains known solutions of General Relativity (GR), and admits solutions that are absent in GR. Here we study cosmological implications of some of these…

High Energy Physics - Theory · Physics 2008-11-26 Gregory Gabadadze , Yanwen Shang

A covariant Lagrangian formulation of a solution to the cosmological constant problem, based on vizualising the fluctuations of the vacuum energy as a non-equilibrium process with stochastic behaviour, is presented. The variational…

Astrophysics · Physics 2016-08-30 J. W. Moffat

Recently, there have been claims in the literature that the cosmological constant problem can be dynamically solved by specific compactifications of gravity from higher-dimensional toy models. These models have the novel feature that in the…

High Energy Physics - Theory · Physics 2016-07-04 Mark P. Hertzberg , Ali Masoumi

For a large region of parameter space involving the cosmological constant and mass parameters, we discuss fluctuating spacetime solutions that are effectively Minkowskian on large time and distance scales. Rapid, small amplitude…

High Energy Physics - Theory · Physics 2009-11-10 T. Hirayama , B. Holdom

A new approach to the cosmological constant problem is proposed by modifying Einstein's theory of general relativity, using instead a scalar-tensor theory of gravitation. This theory of gravity crucially incorporates the concept of quantum…

General Relativity and Quantum Cosmology · Physics 2011-10-28 Thomas L. Wilson

We study a set of static solutions of the Einstein equations in presence of a massless scalar field and establish their connection to the Kantowski-Sachs cosmological solutions based on some kind of duality transformations. The physical…

General Relativity and Quantum Cosmology · Physics 2009-11-11 M. Gaudin , V. Gorini , A. Kamenshchik , U. Moschella , V. Pasquier

A gravity theory without masses can be constructed in Minkowski spaces using a geometric Minkowski potential. The related affine spacelike spheres can be seen as the regions of the Minkowski spacelike vectors characterized by a constant…

General Relativity and Quantum Cosmology · Physics 2019-10-23 Wladimir-Georges Boskoff , Salvatore Capozziello

Recent data on supernovae favor high values of the cosmological constant. Spacetimes with a cosmological constant have non-relativistic kinematics quite different from Galilean kinematics. De Sitter spacetimes, vacuum solutions of…

General Relativity and Quantum Cosmology · Physics 2009-10-31 R. Aldrovandi , A. L. Barbosa , L. C. B. Crispino , J. G. Pereira

Strong field (exact) solutions of the gravitational field equations of General Relativity in the presence of a Cosmological Constant are investigated. In particular, a full exact solution is derived within the inhomogeneous Szekeres-Szafron…

General Relativity and Quantum Cosmology · Physics 2011-07-19 G. V. Kraniotis , S. B. Whitehouse

In absence of matter Einstein gravity with a cosmological constant $\La$ can be formulated as a scale-free theory depending only on the dimensionless coupling constant G \Lambda where G is Newton constant. We derive the conformal field…

High Energy Physics - Theory · Physics 2009-11-11 Mariano Cadoni

The article proposes an amendment to the relativistic continuum mechanics which introduces the relationship between density tensors and the curvature of spacetime. The resulting formulation of a symmetric stress-energy tensor for a system…

General Physics · Physics 2023-12-19 Piotr Ogonowski

In this work, we seek a cosmological mechanism that may define the sign of the effective gravitational coupling constant, {\em G}. To this end, we consider general scalar-tensor gravity theories as they provide the field theory natural…

General Relativity and Quantum Cosmology · Physics 2019-03-19 Ismael Ayuso , José P. Mimoso , Nelson J. Nunes

Based on the assertion that the cosmological constant problem is essentially a quantum gravity problem, the framework which addresses the cosmological constant problem should also bear a picture for the ``quantum space-time''. In this talk…

High Energy Physics - Phenomenology · Physics 2009-10-07 M. M. Sheikh-Jabbari