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A model one-dimensional self consistent steady state collisionless self-gravitating system in which all the particles have the same energy is presented. This has the remarkable property that the position and velocity of the particles…

Astrophysics of Galaxies · Physics 2026-01-07 Rajaram Nityananda

In 1990 Senovilla$^1$ obtained an interestisng cosmological solution of Einstein's equations that was free of the big-bang singularity. It represented an inhomogeneous and anisotropic cylindrical model filled with disordered radiation,…

General Relativity and Quantum Cosmology · Physics 2007-05-23 N. Dadhich , R. Tikekar , L. K. Patel

We show that for generic sliced spacetimes global hyperbolicity is equivalent to space completeness under the assumption that the lapse, shift and spatial metric are uniformly bounded. This leads us to the conclusion that simple sliced…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Spiros Cotsakis

We study static spherically symmetric solutions to Einstein's equations with a repulsive singularity at the centre. We show that geodesics are extendible across the singularity, so the singularity does not lead to pathological causality…

General Relativity and Quantum Cosmology · Physics 2018-02-14 Ntina Savvidou , Charis Anastopoulos

A new solution of the Einstein-Born-Infeld theory in 2+1 space-time is derived. A new solution has no horizon there are two singularity. This space-time has two singular points, however, one of the point at the origin is not in the physical…

General Relativity and Quantum Cosmology · Physics 2014-02-14 Masashi Kuniyasu

This talk is about solving cosmological equations analytically without approximations, and discovering new phenomena that could not be noticed with approximate solutions. We found all the solutions of the Friedmann equations for a specific…

General Relativity and Quantum Cosmology · Physics 2011-09-30 Itzhak Bars

We consider globally hyperbolic spacetimes with compact Cauchy surfaces in a setting compatible with the presence of a positive cosmological constant. More specifically, for 3+1 dimensional spacetimes which satisfy the null energy condition…

General Relativity and Quantum Cosmology · Physics 2018-03-13 Gregory J. Galloway , Eric Ling

We study five dimensional(5D) spherically symmetric self-similar perfect fluid space-time with adiabatic equation of state, considering all the families of future directed non-spacelike geodesics. The space-time admits globally strong…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Sanjay B. Sarwe , R. V. Saraykar

We consider spacetimes consisting of a manifold with Lorentzian metric and a weight function or scalar field. These spacetimes admit a Bakry-\'Emery-Ricci tensor which is a natural generalization of the Ricci tensor. We impose an energy…

Differential Geometry · Mathematics 2015-10-28 Gregory J. Galloway , Eric Woolgar

Sufficient conditions for the well-posedness of the initial value problem for the scalar wave equation are obtained in space-times with hypersurface singularities

General Relativity and Quantum Cosmology · Physics 2009-09-25 J. A. Vickers , J. P. Wilson

In this paper and the companion paper [EJE2], we establish finite-time singularity formation for finite-energy strong solutions to the axi-symmetric $3D$ Euler equations in the domain $\{(x,y,z)\in\mathbb{R}^3:z^2\leq c(x^2+y^2)\}$ for some…

Analysis of PDEs · Mathematics 2017-12-27 Tarek M. Elgindi , In-Jee Jeong

We construct local, in spacetime, singular solutions to the Einstein vacuum equations that exhibit Kasner-like behavior in their past boundary. Our result can be viewed as a localization (in space) of the construction in \cite{FL}. We also…

Analysis of PDEs · Mathematics 2024-12-24 Nikolaos Athanasiou , Grigorios Fournodavlos

We consider solutions to the hyperbolic system of equations of ideal granular hydrodynamics with conserved mass, total energy and finite momentum of inertia and prove that these solutions generically lose the initial smoothness within a…

Analysis of PDEs · Mathematics 2015-05-28 Olga Rozanova

We study a model of a scalar field minimally coupled to gravity, with a specific potential energy for the scalar field, and include curvature and radiation as two additional parameters. Our goal is to obtain analytically the complete set of…

High Energy Physics - Theory · Physics 2013-05-30 Itzhak Bars , Shih-Hung Chen , Paul J. Steinhardt , Neil Turok

Singularity theorems demonstrate the inevitable breakdown of the concept of continuous, classical spacetime under highly general conditions. Quantum gravity is expected to intervene to avoid singularities and models so far hint towards…

General Relativity and Quantum Cosmology · Physics 2024-08-30 Raúl Carballo-Rubio , Stefano Liberati , Vania Vellucci

This work is essentially a review of a new spacetime model with closed causal curves, recently presented in another paper (Class. Quantum Grav. \textbf{35}(16) (2018), 165003). The spacetime at issue is topologically trivial, free of…

General Relativity and Quantum Cosmology · Physics 2021-09-15 Davide Fermi

We review recent work on the existence and nature of cosmological singularities that can be formed during the evolution of generic as well as specific cosmological spacetimes in general relativity. We first discuss necessary and sufficient…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Spiros Cotsakis

Cosmological singularity theorems such as that of Hawking and Penrose assume local curvature conditions as well as global ones like the existence of a compact (achronal) slice. Here, we prove a new singularity theorem for chronological…

General Relativity and Quantum Cosmology · Physics 2019-08-29 Martin Lesourd

We present analytic solutions to a class of cosmological models described by a canonical scalar field minimally coupled to gravity and experiencing self interactions through a hyperbolic potential. Using models and methods inspired by…

High Energy Physics - Theory · Physics 2015-03-19 Itzhak Bars , Shih-Hung Chen , Neil Turok

We prove uniform finite-time existence of solutions to the vacuum Einstein equations in polarized U(1) symmetry which have uniformly positive incoming $H^1$ energy supported on an arbitrarily small set in the 2 + 1 spacetime obtained by…

General Relativity and Quantum Cosmology · Physics 2024-06-14 Spyros Alexakis , Nathan Thomas Carruth