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We report on a new two-parameter class of cosmological solutions to the Einstein-Maxwell equations. The solutions have everywhere regular curvature invariants. We prove that the solutions are geodesically complete and globally hyperbolic.

General Relativity and Quantum Cosmology · Physics 2009-11-07 Stoytcho Yazadjiev , Ventseslav Rizov

The Galilean gravitation derives from a scalar potential and a vector one. Poisson's equation to determine the scalar potential has no the expected Galilean covariance. Moreover, there are three missing equations to determine the potential…

General Relativity and Quantum Cosmology · Physics 2020-04-08 Géry de Saxcé

We are concerned with the global existence of finite-energy entropy solutions of the one-dimensional compressible Euler equations with (possibly) damping, alignment forces, and nonlocal interactions: Newtonian repulsion and quadratic…

Analysis of PDEs · Mathematics 2024-03-14 Jose A. Carrillo , Gui-Qiang G. Chen , Difan Yuan , Ewelina Zatorska

The discovery of the accelerated expansion of the universe highlighted General Relativity's inability to naturally account for dark energy without invoking a finely tuned cosmological constant. In response, a wide range of alternative…

General Relativity and Quantum Cosmology · Physics 2025-11-11 P. A. G. Monteiro , C. J. A. P. Martins

This paper deals with isothermal Euler-Poisson system which is used to model collapse of self-gravitating Newtonian star. Density dependent viscosity term is added on the right-hand side of momentum equation and it has been proved that…

Analysis of PDEs · Mathematics 2025-08-19 Marko Nedeljkov , Sanja Ružičić

The Einstein-Vlasov-Fokker-Planck system describes the kinetic diffusion dynamics of self-gravitating particles within the Einstein theory of general relativity. We study the Cauchy problem for spatially homogeneous and isotropic solutions…

Analysis of PDEs · Mathematics 2017-10-30 Simone Calogero , Stephen Pankavich

We show that Einstein equations are compatible with the presence of massive point particle idealization and find the corresponding two parameter family of solutions. They are complete defined by the bare mechanical mass $M>0$ and the…

General Relativity and Quantum Cosmology · Physics 2007-05-23 P P Fiziev

The weak-field limit of Einstein--Cartan (EC) relativity is studied. The equations of EC theory are rewritten such that they formally resemble those of Einstein General Relativity (EGR); this allows ideas from post-Newtonian theory to be…

General Relativity and Quantum Cosmology · Physics 2024-05-21 Matthew Maitra , Jeroen Tromp

We study the cosmological evolution of the field equations in the context of Einstein-Aether cosmology by including a scalar field in a spatially flat Friedmann--Lema\^{\i}tre--Robertson--Walker spacetime. Our analysis is separated into two…

General Relativity and Quantum Cosmology · Physics 2020-01-17 Andronikos Paliathanasis , G. Papagiannopoulos , Spyros Basilakos , John D. Barrow

Proceeding from a homogeneous and isotropic Friedmann universe a conceptional problem concerning light propagation in an expanding universe is brought up. As a possible solution of this problem it is suggested that light waves do not scale…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Peter Huber

We investigate multidimensional model for incompressible non-Newtonian fluids. Using method of energy estimates we prove the property of finite speed of propagations of the solution support for this problem. We find sharp bounds of the…

Analysis of PDEs · Mathematics 2007-12-10 Roman Taranets , Yuliya Namlyeyeva

It is shown that Einstein field equations give two solutions for cosmology. The first one is the standard well known representative of the present status of cosmology. We identify it with the local point of view of a flat Universe with the…

General Physics · Physics 2008-01-04 Antonio Alfonso-Faus

Global stability of the spherically symmetric nonisentropic compressible Euler equations with positive density around global-in-time background affine solutions is shown in the presence of free vacuum boundaries. Vacuum is achieved despite…

Analysis of PDEs · Mathematics 2021-06-03 Calum Rickard

Einstein Equivalence Principle (EEP) requires all matter components to universally couple to gravity via a single common geometry: that of spacetime. This relates quantum theory with geometry as soon as interactions with gravity are…

General Relativity and Quantum Cosmology · Physics 2022-09-13 Ashkan Alibabaei

Non-linear nature of Einstein equation introduces genuine relativistic higher order corrections to the usual Newtonian fluid equations describing the evolution of cosmological perturbations. We study the effect of such novel non-linearities…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 Donghui Jeong , Jinn-Ouk Gong , Hyerim Noh , Jai-chan Hwang

The possibility that the strength of gravitational interactions might slowly increase with distance, is explored by formulating a set of effective field equations, which incorporate the gravitational, vacuum-polarization induced, running of…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Herbert W. Hamber , Ruth M. Williams

The Lagrangian fluid description is employed to solve the initial value problem for one-dimensional, compressible fluid flows represented by the Euler-Poisson system. Exact nonlinear and time-dependent solutions are obtained, which exhibit…

Plasma Physics · Physics 2017-09-06 A. R. Karimov , H. Schamel

In this paper, the smooth solution of the physical vacuum problem for the one dimensional compressible Euler equations with time-dependent damping is considered. Near the vacuum boundary, the sound speed is $C^{1/2}$-H\"{o}lder continuous.…

Analysis of PDEs · Mathematics 2022-08-08 Xinghong Pan

In this paper, second post-Newtonian approximation of Einstein-aether theory is obtained by Chandrasekhar's approach. Five parameterized post-Newtonian parameters in first post-Newtonian approximation are presented after a time…

General Relativity and Quantum Cosmology · Physics 2009-02-14 Yi Xie , Tian-Yi Huang

Recently, evidence has been collected that a class of gravitational theories with certain non-local operators is renormalizable. We consider one such model which, at the linear perturbative level, reproduces the effective non-local action…

General Relativity and Quantum Cosmology · Physics 2014-08-26 Gianluca Calcagni , Leonardo Modesto , Piero Nicolini