Blar i TKD - Institutt for informasjonsteknologi på emneord "VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Astrofysikk, astronomi: 438"

Viser treff 1-9 av 9

    • A solution of the Mitra Paradox 

      Grøn, Øyvind (Journal article; Peer reviewed, 2016)
      The “Mitra paradox” refers to the fact that while the de Sitter spacetime appears non-static in a freely falling reference frame, it looks static with reference to a fixed reference frame. The coordinate-independent nature ...

    • Bianchi type-I universe model with nonlinear viscosity 

      Mostafapoor, Nouraddin; Grøn, Øyvind (Journal article; Peer reviewed, 2012-08-23)
      In this paper we study the evolution of spatially homogeneous and anisotropic Bianchi type-I Universe models with the cosmological constant, Λ, and filled with nonlinearviscous fluid. The dynamical equations for these ...

    • Entropy and gravity 

      Grøn, Øyvind (Entropy;14, Journal article; Peer reviewed, 2012-12-04)
      The effect of gravity upon changes of the entropy of a gravity-dominated system is discussed. In a universe dominated by vacuum energy, gravity is repulsive, and there is accelerated expansion. Furthermore, inhomogeneities ...

    • Gravitational Entropy and Inflation 

      Elgarøy, Øystein; Grøn, Øyvind (Entropy;15 (9), Journal article; Peer reviewed, 2013-09-04)
      The main topic of this paper is a description of the generation of entropy at the end of the inflationary era. As a generalization of the present standard model of the Universe dominated by pressureless dust and a Lorentz ...

    • The Cosmic Causal Mass 

      Bræck, Simen; Grøn, Øyvind; Farup, Ivar (Journal article; Peer reviewed, 2017)
      In order to provide a better understanding of rotating universe models, and in particular the Gödel universe, we discuss the relationship between cosmic rotation and perfect inertial dragging. In this connection, the concept ...

    • The twin paradox and the principle of relativity 

      Grøn, Øyvind (Physica Scripta;87(3), Journal article; Peer reviewed, 2013-02-14)
      The twin paradox is intimately related to the principle of relativity. Two twins A and B meet, travel away from each other and meet again. From the point of view of A, B is the traveller. Thus, A predicts B to be younger ...

    • Universe models with negative bulk viscosity 

      Brevik, Iver Håkon; Grøn, Øyvind (Astrophysics and Space Science;347 (2), Journal article; Peer reviewed, 2013-10)
      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. [Science 339, 52 (2013)], where an attractively ...

    • Viscous Lambda CDM universe models 

      Grøn, Øyvind; Mostafapoor, Nouraddin (Astrophysics and Space Science;333 (2), Journal article; Peer reviewed, 2011-03-30)
      We explore flat ACDM models with bulk viscosity, and study the role of the bulk viscosity in the evolution of these universe models. The dynamical equations for these models are obtained and solved for some cases of ...

    • Warm inflation 

      Grøn, Øyvind (Universe;, Journal article; Peer reviewed, 2016)
      I show here that there are some interesting differences between the predictions of warm and cold inflation models focusing in particular upon the scalar spectral index ns and the tensor-to-scalar ratio r. The first thing ...