Radiating black hole solutions in arbitrary dimensions

We prove a theorem that characterizes a large family of non-static solutions to Einstein equations in N-dimensional space-time, representing, in general, spherically symmetric Type II fluid. It is shown that the best known Vaidya-based (radiating) black hole solutions to Einstein equations, in both four dimensions (4D) and higher dimensions (HD), are particular cases from this family. The spherically symmetric static black hole solutions for Type I fluid can also be retrieved. A brief discussion on the energy conditions, singularities and horizons is provided.     

Local Existence and Continuation Criterion for Solutions of the Spherically Symmetric Einstein-Vlasov-Maxwell System

Using the iterative scheme we prove the local existence and uniqueness of solutions of the spherically symmetric Einstein-Vlasov-Maxwell system with small initial data. We prove a continuation criterion to global in-time solutions.     

Neutrinos for geophysics

The Mikheyev-Smirnov-Wolfenstein solution to the solar-neutrino deficit provides a range for the acceptable neutrino parameters (Δm² and sin 2θ₀). If the vacuum mixing angle θ₀ is not too small, the resulting neutrino oscillation length in matter is comparable to the radius of the earth. For such appropriate neutrino parameters we study neutrino oscillations inside the earth. The core of the earth is taken as a sphere with constant density 11 g/cm³, while the mantle, surrounding the core, is taken to be a spherically symmetric shell of constant density 4.4 g/cm³. We obtain an exact, analytic expression for the probability that an electron-neutrino after traversing the earth, emerges as an electron-neutrino. Our results indicate that the neutrinos might serve as the ideal tools for earth tomography.     

Global spherically symmetric solutions to the equations of a viscous polytropic ideal gas in an exterior domain

We consider the equations of a viscous polytropic ideal gas in the domain exterior to a ball in ⁿ (n=2 or 3) and prove the global existence of spherically symmetric smooth solutions for (large) initial data with spherical symmetry. The large-time behavior of the solutions is also discussed. To prove the existence we first study an approximate problem in a bounded annular domain and then obtain a priori estimates independent of the boundedness of the annular domain. Letting the diameter of the annular domain tend to infinity, we get a global spherically symmetric solution as the limit.Dedicated to Professor Rolf Leis on the occasion of his 65th birthdaySupported by the SFB 256 of the Deutsche Forschungsgemeinschaft at the University of Boon.     

The Newtonian limit of the spherically symmetric Vlasov-Einstein system

We prove that spherically symmetric solutions of the Vlasov-Einstein system with a fixed initial value converge to the corresponding solution of the Vlasov-Poisson system if the speed of lightc is taken as a parameter and tends to infinity. The convergence is uniform on compact time intervals with convergence rate 1/c ². Thus the classical Vlasov-Poisson system appears as the Newtonian limit of the general relativistic Vlasov-Einstein system in a spherically symmetric setting.     

On Existence of Mini-Boson Stars

We prove the existence of a countable family of globally regular solutions of spherically symmetric Einstein–Klein–Gordon equations. These solutions, known as mini-boson stars, were discovered numerically many years ago. Received: 14 February 2000 / Accepted: 26 June 2000     

The asymptotic behavior of Yang-Mills fields in the large

We consider Yang-Mills fields in Minkowski space-time and prove that all spherically symmetric solutions in the canonical gauge decay in time, provided the initial data has finite conformal energy.Work supported by Sonderforschungsbereich 256 of the Deutsche Forschungsgemeinschaft     

Existence of Axially Symmetric Static Solutions of the Einstein-Vlasov System

We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.     

The existence of multi-monopole solutions to the non-Abelian,Yang-Mills-Higgs Equations for arbitrary simple gauge groups

We prove that for arbitrary simple gauge groups, the non-Abelian Yang-Mills-Higgs Equations on ³ in the Prasad-Sommerfield limit have at least a countably infinite set of distinct solutions. These solutions may be interpreted physically as configurations of widely spaced, non-interacting fundamental monopoles. The solutions are generically not spherically symmetric.Harvard University, John Parker FellowThis work is supported in part by the National Science Foundation under Grant No. PHY 79-16812     

球对称的SU2规范场和磁单极的规范场描述

本文讨论球对称的SU₂规范场,证明了满足最一般的球对称定义的SU₂规范场只能有三种基本类型:(1)同步球对称规范场;(2)狭义球对称规范场;(3)化约为U₁子群的球对称规范场。文中详细讨论了球对称的带同位旋向量场(Higgs场)的SU₂规范场,完全决定了它们的类型。如果把这种场看成为由电磁场和带电矢介子构成,那末就有如下的结论:如果磁单极所含的磁荷是最小单位的m倍,当|m|>1时,球对称的带Higgs场的SU₂规范场只能是纯电磁场,而不能有带电矢介子场出现。但当m=0,±1时,球对称的带电矢介子场是可以出现的。从而可见,具有非单位磁荷的磁单极隐含了某种破坏球对称的因素。     

The Dynamical Instability of Static, Spherically Symmetric Solutions in Nonsymmetric Gravitational Theories

We consider the dynamical stability of a class of static, spherically symmetric solutions of the nonsymmetric gravitational theory. We numerically reproduce the Wyman solution and generate new solutions for the case where the theory has a nontrivial fundamental length scale ^-1. By considering spherically symmetric perturbations of these solutions we show that the Wyman solutions are generically unstable.     

On Spherically Symmetric Solutions¶of the Compressible Isentropic Navier–Stokes Equations

We prove the global existence of weak solutions to the Cauchy problem for the compressible isentropic Navier–Stokes equations in ℝ ⁿ (n= 2, 3) when the Cauchy data are spherically symmetric. The proof is based on the exploitation of the one-dimensional feature of symmetric solutions and use of a new (multidimensional) property induced by the viscous flux. The present paper extends Lions' existence theorem [15] to the case 1< γ <γ _n for spherically symmetric initial data, where γ is the specific heat ratio in the pressure, γ _n = 3/2 for n= 2 and γ _n = 9/5 for n= 3. Dedicated to Professor Rolf Leis on the occasion of his 70th birthday Received: 17 January 2000 / Accepted: 3 July 2000     

Birkhoff theorem and matter

Birkhoff’s theorem for spherically symmetric vacuum spacetimes is a key theorem in studying local systems in general relativity theory. However realistic local systems are only approximately spherically symmetric and only approximately vacuum. In a previous paper, we showed the theorem remains approximately true in an approximately spherically symmetric vacuum space time. In this paper we prove the other case: the theorem remains approximately true in a spherically symmetric, approximately vacuum space time.     

Axially symmetric solutions generated by the complexification technique

Banerjee and Andrade generated axially symmetric electrovac solutions from the spherically symmetric Reissner-Nordström solution by giving a complex translation along theZ axis. We use the same method for generating new more complicated axially symmetric solutions from known solutions. Several such examples are given.     

Inconsistencies in four-dimensional Einstein-Gauss-Bonnet gravity

We attempt to clarify several aspects concemi ng the recently presented four-dimensional Ein stein-Gauss-Bonnet gravity.We argue that the limiting procedure outlined in[Phys.Rev.Lett.124,081301(2020)]generally involves ill-defined terms in the four dimensional field equations.Potential ways to circumvent this issue are discussed,alongside remarks regarding specific solutions of the theory.We prove that,although linear perturbations are well behaved around maximally symmetric backgrounds,the equations for second-order perturbations are illdefined even around a Minkowskia n background.Additi on ally,we perform a detailed analysis of the spherically symmetric solutions and find that the central curvature singularity can be reached within a finite proper time.     

Dipole transition matrix elements for certain classes of potential models

We prove results about vanishing and nonvanishing of radial dipole matrix elements for certain classes of spherically symmetric potentials. A basic tool is a new sum rule based on Ehrenfest's law and the superposition principle for solutions of the Schrödinger equation.     

Domain with Noncompactified Extra Dimensions in the Multidimensional Universe with Compactified Extra Dimensions

It is argued that in our Universe with compactified extra dimensions (ED) also domains exist with noncompactified ED. The multidimensional gravity (MD) on the principal bundle with structural group SU(3) is considered and a spherically symmetric solution in this theory is obtained. This solution is a wormhole-like object located between two null surfaces ds² = 0 and can be considered as a domain with noncompactified ED which is sewn to a 4D spacetime with compactified ED. In some sense these solutions are dual to black holes: they represent static spherically symmetric solutions under null surfaces, whereas black holes are static spherically symmetric solutions outside the event horizon.     

Geometric obstruction of black holes

We study the global structure of Lorentzian manifolds with partial sectional curvature bounds. In particular, we prove completeness theorems for homogeneous and isotropic cosmologies as well as static spherically symmetric spacetimes. The completeness of the latter is then employed to rigorously prove the absence of static spherically symmetric black holes in more than three dimensions. The proof of these new results is preceded by a pedagogic review of the local aspects of sectional curvature bounds for Lorentzian manifolds, which extends and strengthens previous constructions.     

Inconsistence of Non-Singular Spherically Symmetric Solution and a Satisfactory Energy-Momentum Complex

Two spherically symmetric non-singular black hole solutions in MØller tetrad theory of gravitation have been obtained. Although the two solutions have the same form of metric (spherically symmetric nonsingular black hole), their energy contents are different. We use another method given by Gibbons andHawking to calculate the energy content of these solutions. We alsoobtained different value of energy. Study the requirements of a satisfactory energy-momentum complex given by MØller we find that the second solution, which behaves as 1/r^1/2, is not transformed as a four-vector under Lorentz transformation.     

Generation and construction of statistical spherically symmetric solutions of the gravitational equations

We show that the possibility of reducing the Einstein equations in isotropic Bondi coordinates for a spherically symmetric statistical case to two forms of a linear differential equation allows one to introduce procedures for generating a fortiori exact solutions of the gravitational equations from the known ones. A superposition of solutions is defined in a special way. Examples are given of the known solutions obtained in this way from flat space-time. The use of the proposed generating procedures allows one to find all exact solutions of the gravitational equations for neutral sources in the statistical, spherically symmetric case.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 5–9, June, 1990.