41 citations · 162 across the 14 of their papers we have counts for
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Anisotropic Generalization of the ΛCDM Universe Model with Application to the Hubble Tension
Øyvind G. Grøn
I deduce an exact and analytic Bianchi type I solution of Einsteins field equations, which generalizes the isotropic LambdaCDM universe model to a corresponding model with anisotro…
Relativistic Viscous Universe Models
Iver Brevik, Øyvind Grøn
The research on relativistic universe models with viscous fluids is reviewed. Viscosity may have been of significance during the early inflationary era, and may also be of importan…
A source of the C-metric with perfect translational inertial dragging
Brynjar Arnfinnsson, Øyvind Grøn
A new source of the C-metric is described using Israel's formalism. This source is a singular accelerated shell. By construction, perfect inertial dragging is realized inside the s…
Universe Models with Negative Bulk Viscosity
Iver Brevik, Øyvind Grøn
The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. [Scien…
A river model of space
S. Braeck, O. Gron
Within the theory of general relativity gravitational phenomena are usually attributed to the curvature of four-dimensional spacetime. In this context we are often confronted with…
A spacetime with closed timelike geodesics everywhere
Oyvind Gron, Steinar Johannesen
In the present article we find a new class of solutions of Einstein's field equations. It describes stationary, cylindrically symmetric spacetimes with closed timelike geodesics ev…
FRW Universe Models in Conformally Flat Spacetime Coordinates
Oyvind Gron, Steinar Johannesen
The 3-space of a universe model is defined at a certain simultaneity. Hence space depends on which time is used. We find a general formula generating all known transformations to c…
Optics in a field of gravity
E. Eriksen, O. Gron
An observer at rest in a uniformly accelerated reference frame experiences a parallel gravitational field, where the rays of light are formed as circular arcs instead of being stra…
Singular shell embedded into a cosmological model
Oyvind Gron, Peter D. Rippis
We generalize Israel's formalism to cover singular shells embedded in a non-vacuum Universe. That is, we deduce the relativistic equation of motion for a thin shell embedded in a S…
Gravitational Entropy and Quantum Cosmology
O. Gron, S. Hervik
We investigate the evolution of different measures of ``Gravitational Entropy'' in Bianchi type I and Lemaître-Tolman universe models. A new quantity behaving in accordance with th…