• A relativistic trolley paradox 

      Matvejev, Vadim; Matvejev, Oleg; Grøn, Øyvind (Journal article; Peer reviewed; Journal article, 2016-02)
      We present an apparent paradox within the special theory of relativity, involving a trolley with relativistic velocity and its rolling wheels. Two solutions are given, both making clear the physical reality of the Lorentz ...
    • 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 ...
    • An interesting consequence of the general principle of relativity 

      Grøn, Øyvind; Jemterud, Torkild (Journal article; Peer reviewed; Journal article, 2016-04-12)
      We show that Einstein s general theory of relativity, together with the a ssumption that the prin- ciple of relativity encompasses rotational motion, predicts that in a flat Friedmann-Lemaitre-Robertson- Walker (FLRW) ...
    • Atmospheric and Ocean Dynamics May Explain Cycles in Oceanic Oscillations 

      Seip, Knut Lehre; Grøn, Øyvind (Climate;Volume 7 / Issue 6, Journal article; Peer reviewed, 2019-05-29)
      What causes cycles in oceanic oscillations, and is there a change in the characteristics of oscillations in around 1950? Characteristics of oceanic cycles and their sources are important for climate predictability. We here ...
    • 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 ...
    • Carbon dioxide precedes temperature change during short-term pauses in multi-millennial palaeoclimate records 

      Seip, Knut Lehre; Grøn, Øyvind; Wang, Hui (Palaeogeography, Palaeoclimatology, Palaeoecology;Volume 506, 1 October 2018, Journal article; Peer reviewed, 2018-06-19)
      In Antarctica, ice-core temperature has traditionally been regarded as a leading variable to carbon dioxide, CO⁠2 during the last 400,000years before present (B.P.). This finding is in contrast to most reports on global ...
    • Celebrating the centenary of the Schwarzschild solutions 

      Grøn, Øyvind (Peer reviewed; Journal article; Journal article, 2016)
      This article is a celebration of the centenary of Schwarzschild’s presentations of his external and internal solutions describing spacetime outside and inside an incompressible, spherically symmetric body. I ...
    • Cycles in oceanic teleconnections and global temperature change 

      Seip, Knut Lehre; Grøn, Øyvind (Theoretical and Applied Climatology;, Journal article; Peer reviewed, 2018-06-11)
      Three large ocean currents are represented by proxy time series: the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI), and the Pacific Decadal Oscillation (PDO).We here show how proxies for the ...
    • Different representations of the Levi-Civita Bertotti Robinson solution 

      Grøn, Øyvind; Johannesen, Steinar (The European Physical Journal Plus;128, Journal article; Peer reviewed, 2013-04-23)
      The Levi-Civita Bertotti Robinson (LBR) spacetime is investigated in various coordinate systems. By means of a general formalism for constructing coordinates in conformally flat spacetimes, coordinate transformations ...
    • The discovery of the expansion of the universe 

      Grøn, Øyvind (Galaxies;Volume 6, Issue 4, Journal article; Journal article; Peer reviewed, 2018-12-03)
      Alexander Friedmann, Carl Wilhelm Wirtz, Vesto Slipher, Knut E. Lundmark, Willem de Sitter, Georges H. Lemaître, and Edwin Hubble all contributed to the discovery of the expansion of the universe. If only two persons are ...
    • Electrodynamics of Radiating Charges 

      Grøn, Øyvind (Advances in Mathematical Physics;, Journal article; Peer reviewed, 2012)
      The theory of electrodynamics of radiating charges is reviewed with special emphasis on the role of the Schott energy for the conservation of energy for a charge and its electromagnetic field. It is made clear that the ...
    • 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 ...
    • Exact Solutions of the Field Equations for Empty Space in the Nash Gravitational Theory 

      Aadne, Matthew Terje; Grøn, Øyvind (Universe;Volume 3, Issue 1, Journal article; Peer reviewed, 2017-02-14)
      John Nash has proposed a new theory of gravity. We define a Nash-tensor equal to the curvaturetensorappearingintheNashfieldequationsforemptyspace,andcalculateitscomponents for two cases: 1. A static, spherically symmetric ...
    • Generalizations of the Levi-Civita-Bertotti-Robinson spacetime 

      Grøn, Øyvind; Johannesen, Steinar (The European Physical Journal Plus;129(10), Journal article; Peer reviewed, 2014-10-22)
      The Levi-Civita-Bertotti-Robinson (LBR) solution of Einstein's field equations may be interpreted to describe spacetime in a region without matter outside a charged spherical domain wall. In the present paper we investigate ...
    • 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 ...
    • Leading the game, losing the competition: identifying leaders and followers in a repeated game 

      Seip, Knut Lehre; Grøn, Øyvind (Journal article; Peer reviewed, 2016)
      We explore a new method for identifying leaders and followers, LF, in repeated games by analyzing an experimental, repeated (50 rounds) game where Row player shifts the payoff between small and large values – a type of ...
    • A new method for identifying possible causal relationships between CO2, total solar irradiance and global temperature change 

      Seip, Knut Lehre; Grøn, Øyvind (Theoretical and Applied Climatology;2015, Journal article; Peer reviewed, 2015-11-20)
      We apply a novel method based upon “before” and “after” relationships to investigate and quantify interconnections between global temperature anomaly, GTA, as response variable, and greenhouse gases, CO2, and total solar ...
    • The North Atlantic oscillations: cycle times for the NAO, the AMO and the AMOC 

      Seip, Knut Lehre; Grøn, Øyvind; Wang, Hui (Climate;Volume 7, Issue 3, Journal article; Peer reviewed, 2019-03-19)
      We show that oceanic cycle lengths persist across oceanic cyclic time-series by comparing cycles in series that come from “sister” measurements in the North Atlantic Ocean. These are the North Atlantic oscillation (NAO), ...
    • On the Global Navigation Satellite Systems and Relativity 

      Gjevestad, Jon Glenn; Grøn, Øyvind (Kart og Plan;73 (1), Journal article; Peer reviewed, 2013)
      GNSS, or more precisely GNSS-2, is an abbreviation for Glob al Navigation Satellite Systems – Second generation, and serves as a generic name for the class of modern global sa tellite based radio navigation systems. ...
    • On the relativity of rotation 

      Grøn, Øyvind (Nuovo cimento. B;(7), Journal article; Peer reviewed, 2010)
      The question whether rotational motion is relative according to the general theory of relativity is discussed. Einstein’s ambivalence concerning this question is pointed out. In the present article I defend Einstein’s way ...