A note on Browne's “source function” in five-dimensional relativityGeneral Relativity and Gravitation - Tập 13 - Trang 495-501 - 1981
B. T. McInnes
One of the postulates of the Kaluza-Klein theory is that the lines representing events should be geodesics. Recently a claim has been made that in the Jordan-Thiry version of the theory, this is not only unnecessary, but in fact contradicts experiment. It is the purpose of the present note to show that this conclusion is in error and to point out an undesirable feature of the entire Jordan-Thiry p...... hiện toàn bộ
Abelian 2+1D loop quantum gravity coupled to a scalar fieldGeneral Relativity and Gravitation - Tập 51 - Trang 1-48 - 2019
Christoph Charles
In order to study 3d loop quantum gravity coupled to matter, we consider a simplified model of abelian quantum gravity, the so-called
$$\mathrm {U}(1)^3$$
model. Abelian gravity coupled to a scalar field shares a lot of commonalities with paramet...... hiện toàn bộ
Testing general relativity with cosmological large scale structureGeneral Relativity and Gravitation - Tập 54 - Trang 1-19 - 2022
Ruth Durrer
In this paper I investigate the possibility to test Einstein’s equations with observations of cosmological large scale structure. I first show that we have not tested the equations in observations concerning only the homogeneous and isotropic Universe. I then show with several examples how we can do better when considering the fluctuations of both, the energy momentum tensor and the metric. This i...... hiện toàn bộ
Modified No-hair Conjecture and the Limiting ProcessGeneral Relativity and Gravitation - - 1998
K. K. Nandi, S. M. K. Alam, B. Bhattacharjee, J. Evans
It is argued that the Schwarzschild black hole solution follows as a unique limit of the Brans-Dicke Class I solutions, provided the correct iterated limit is taken. Such a uniqueness is essential for the validity of a recent version of the no-hair conjecture. A non-trivial modification to this version is proposed in order to exclude Brans-Dicke Class IV solutions which appear to represent scalar ...... hiện toàn bộ
Tachyons and the second law of black hole physicsGeneral Relativity and Gravitation - Tập 9 - Trang 1089-1100 - 1978
S. V. Dhurandhar, J. V. Narlikar
It is shown that the usual proof of the second law of black hole physics breaks down if there are tachyons present in the vicinity of a black hole. Explicit cases are discussed where a tachyon of positive energy falling into the Kerr singularity actually decreases the area of the Kerr black hole.
The homogeneity of the universeGeneral Relativity and Gravitation - Tập 11 - Trang 281-289 - 1979
G. F. R. Ellis
The observational and philosophical grounds for our belief in the spatial homogeneity of the universe, are reconsidered. On the one hand, spatial homogeneity cannot be directly verified observationally, and, on the other hand, it raises a series of philosophical problems that counter its attractiveness to a considerable degree. It is pointed out that there are several possible alternative approach...... hiện toàn bộ
On the stability of electrostatics stars with modified non-gauge invariant Einstein-Maxwell gravityGeneral Relativity and Gravitation - Tập 55 - Trang 1-21 - 2023
H. Ghaffarnejad, T. Ghorbani, F. Eidizadeh
We use a modified Einstein-Maxwell gravity to study stability of an electrostatic spherical star. Correction terms in this model are scalars which are made from contraction of Ricci tensor and electromagnetic vector potential. Our motivation to use this kind of exotic Einstein-Maxwell gravity is inevitable influence of cosmic magnetic field in inflation of the universe which is observed now but it...... hiện toàn bộ
Particle Creation in Cosmological Models with Varying Gravitational and Cosmological “Constants”General Relativity and Gravitation - Tập 31 - Trang 849-862 - 1999
T. Harko, M. K. Mak
Einstein's field equations with variablegravitational coupling G = G(t) and decaying vacuumenergy density Λ = Λ(t) are considered asdescribing matter creation in a cosmological framework.The particle creation rate is determined by thevariation rate of both G and Λ. By consideringsimple phenomenological evolution laws for G and Lambda,an exact solution of the gravitational field equationsfor a flat...... hiện toàn bộ