General Relativity and Gravitation
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The homogeneity of the universe
General Relativity and Gravitation - Tập 11 - Trang 281-289 - 1979
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......
Dynamics of the universe with variable parameters that govern the gravitational interactions
General Relativity and Gravitation - Tập 56 - Trang 1-26 - 2024
The present study investigates the Friedmann–Lemaitre–Robertson–Walker models (often FLRW models) with time varying G and
$$\Lambda $$
in the general theory of relativity. In this communication the Einstein field equations have been solved by considering the deceleration parameter q(t) as a varyin......
Letter: Effects of a Torsion Field on Big Bang Nucleosynthesis
General Relativity and Gravitation - Tập 31 - Trang 1935-1939 - 1999
In this paper we investigate whether torsion,which arises naturally in most theories of quantumgravity, has observable implications for the Big Bangnucleosynthesis. Torsion can lead to spin flips amongst neutrinos thus turning them into sterileneutrinos. In the early Universe they can alter thehelium abundance which is tightly constrained byobservations. Here I calculate to what extent torsion oft......
Circular orbits and relative strains in Schwarzschild space-time
General Relativity and Gravitation - Tập 24 - Trang 1091-1100 - 1992
The equation of the relative strain is analyzed in tetrad form with respect to a family of observers moving on spatially circular orbits, in the Schwarzschild space-time. We select a field of tetrads, which we term phase locking frames, and explicitly calculate how, in the equatorial plane, the orbital acceleration, its gradient and the Fermi drag add together to compensate the curvature and assur......
Erratum to: A set of invariant quality factors measuring the deviation from the Kerr metric
General Relativity and Gravitation - Tập 45 Số 6 - Trang 1129-1129 - 2013
Einstein-Rosen metrics generated by the inverse scattering transform
General Relativity and Gravitation - Tập 18 - Trang 1141-1158 - 1986
The most general Einstein-Rosen solutions obtainable by the inverse scattering transform, using the Levi-Cività metric as seed are analyzed. They can be classified as a family of evolving metrics without a clear physical interpretation and a family representing gravitational waves absorbed and radiated by a massive cylinder. The physical interpretation is based on a perturbative analysis, which sh......
Thermodynamic Equilibrium in the Expanding Universe
General Relativity and Gravitation - Tập 31 - Trang 1395-1405 - 1999
We show that a relativistic gas may be at"global" equilibrium in the expanding universe for anyequation of state 0 < p ≤ ρ/3, provided thatthe gas particles move under the influence of aself-interacting, efiective one-particle force in between elasticbinary collisions. In the force-free limit we recoverthe equilibrium conditions for ultrarelativistic matterwhich imply the existence of a conformal ......
Sobolev stability of the Positive Mass Theorem and Riemannian Penrose Inequality using inverse mean curvature flow
General Relativity and Gravitation - Tập 51 - Trang 1-32 - 2019
We study the Sobolev stability of the Positive Mass Theorem and the Riemannian Penrose Inequality in the case where a region of a sequence of manifolds
$$M^3_i$$
can be foliated by a smooth solution of inverse mean curvature flow (IMCF) which is ......
Einstein–Rosen solutions from Kaluza–Klein theory
General Relativity and Gravitation - Tập 45 - Trang 27-39 - 2012
From a time-dependent boost-rotational symmetric vacuum solution of the Einstein Equations in five dimensions, through the Kaluza–Klein reduction the corresponding Einstein–Maxwell-dilaton solutions are obtained. The four dimensional counterpart turns out to be generalized Einstein–Rosen spacetimes representing unpolarized gravitational waves traveling in an inhomogeneous cosmology. Restricting th......
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