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We consider the classical initial and boundary value problem for the Cahn--Hilliard equation with non-degenerate mobility and singular (e.g., logarithmic) potential. We prove that any weak solution converges to a single equilibrium using…

Analysis of PDEs · Mathematics 2026-02-06 Maurizio Grasselli , Andrea Poiatti

The classical singularity theorems of General Relativity rely on energy conditions that are easily violated by quantum fields. Here, we provide motivation for an energy condition obeyed in semiclassical gravity: the smeared null energy…

General Relativity and Quantum Cosmology · Physics 2021-10-25 Eleni-Alexandra Kontou , Ben Freivogel , Dimitrios Krommydas

In this paper, we discuss the self-consistency condition for the spherical symmetric Klein-Gordon equation, and then discuss a natural possibility that gravity and weak coupling constants g_G and g_W may be defined after g_{EM}. In this…

High Energy Physics - Theory · Physics 2016-09-06 Miyuki Nishikawa

Hawking's singularity theorem says that cosmological solutions arising from initial data with positive mean curvature have a past singularity. However, the nature of the singularity remains unclear. We therefore ask: If the initial…

General Relativity and Quantum Cosmology · Physics 2026-03-03 Hans Oude Groeniger , Oliver Petersen , Hans Ringström

A rigidity theorem that applies to smooth electrovac spacetimes which represent either (A) an asymptotically flat stationary black hole or (B) a cosmological spacetime with a compact Cauchy horizon ruled by closed null geodesics was given…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Istvan Racz

Consider the Klein-Gordon equation (KGE) in $\R^n$, $n\ge 2$, with constant or variable coefficients. We study the distribution $\mu_t$ of the random solution at time $t\in\R$. We assume that the initial probability measure $\mu_0$ has zero…

Mathematical Physics · Physics 2009-11-11 T. V. Dudnikova , A. I. Komech , E. A. Kopylova , Yu. M. Suhov

In the mathematical physics literature, there are heuristic arguments, going back three decades, suggesting that for an open set of initially smooth solutions to the Einstein-vacuum equations in high dimensions, stable, approximately…

Analysis of PDEs · Mathematics 2018-04-19 Igor Rodnianski , Jared Speck

Assuming the Bousso bound, we prove a singularity theorem: if the light rays entering a hyperentropic region contract, then at least one light ray must be incomplete. "Hyperentropic" means that the entropy of the region exceeds the…

High Energy Physics - Theory · Physics 2022-06-22 Raphael Bousso , Arvin Shahbazi-Moghaddam

Two spatial regions $B$ and $R$ are hyperentangled if the generalized entropy satisfies $S_{\text{gen}}^{B\cup R}<S_{\text{gen}}^R$. If in addition all future (or all past) directed inward null shape deformations of $B$ decrease…

High Energy Physics - Theory · Physics 2023-03-30 Raphael Bousso , Arvin Shahbazi-Moghaddam

The singularity theorems of Penrose, Hawking, and Geroch predict the existence of incomplete inextendible causal geodesics in a wide range of physically adequate spacetimes modeling the gravitational collapse of stars and the expanding…

General Relativity and Quantum Cosmology · Physics 2023-01-03 István Rácz

The original singularity theorems of Penrose and Hawking were proved for matter obeying the Null Energy Condition or Strong Energy Condition respectively. Various authors have proved versions of these results under weakened hypotheses, by…

General Relativity and Quantum Cosmology · Physics 2020-04-08 Christopher J. Fewster , Eleni-Alexandra Kontou

The work shows that the evolution of the field of the free Klein-Gordon equation (KGE), in the hydrodynamic representation, can be represented by the motion of a mass density subject to the Bohm-type quantum potential, whose equation can be…

General Physics · Physics 2019-04-10 Piero Chiarelli

As Einstein's gravity is a non-renormalizable theory, it can be a good description of physics only at the scales of energy or spacetime curvature below the Planck mass. Moreover, it requires the presence of an infinite tower of…

General Relativity and Quantum Cosmology · Physics 2025-08-22 Ziyue Zhu , Alexey S. Koshelev , Yang Liu , Anna Tokareva

The energy conditions of Einstein gravity (classical general relativity) are designed to extract as much information as possible from classical general relativity without enforcing a particular equation of state for the stress-energy. This…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Matt Visser

We examine the Einstein equation coupled to the Klein-Gordon equation for a complex-valued scalar field. These two equations together are known as the Einstein-Klein-Gordon system. In the low-field, non-relativistic limit, the…

General Relativity and Quantum Cosmology · Physics 2015-07-10 Andrew S. Goetz

Hawking's black hole area theorem was proven using the null energy condition (NEC), a pointwise condition violated by quantum fields. The violation of the NEC is usually cited as the reason that black hole evaporation is allowed in the…

General Relativity and Quantum Cosmology · Physics 2023-03-14 Eleni-Alexandra Kontou , Veronica Sacchi

We consider the Klein-Gordon system posed in an inhomogeneous medium with smooth boundary subject to a local viscoelastic damping distributed around a neighborhoodof the boundary according to the Geometric Control Condition. We show that…

Improving a singularity theorem in General Relativity by Galloway and Ling we show the following (cf.\ Theorem 1): If a globally hyperbolic spacetime $M$ satisfying the null energy condition contains a closed, spacelike Cauchy surface…

General Relativity and Quantum Cosmology · Physics 2026-03-30 Eric Ling , Carl Rossdeutscher , Walter Simon , Roland Steinbauer

The Gannon-Lee singularity theorems give well-known restrictions on the spatial topology of singularity-free (i.e., nonspacelike geodesically complete), globally hyperbolic spacetimes. In this paper, we revisit these classic results in the…

General Relativity and Quantum Cosmology · Physics 2014-11-21 I. P. Costa e Silva

We study the semiclassical Einstein field equations with a Klein-Gordon field in ultrastatic and static spacetimes. In both cases, the equations for the spacetime metric become constraint equations. In the ultrastatic case, the Hadamard…

General Relativity and Quantum Cosmology · Physics 2021-11-01 Benito A. Juárez-Aubry