Øystein Elgarøy

• Elgarøy, Øystein & Grøn, Øyvind (2013). Gravitational Entropy and Inflation. Entropy.  ISSN 1099-4300.  15, s 3620- 3639 . doi: 10.3390/e15093620 Fulltekst i vitenarkiv.
• Bræck, Simen & Elgarøy, Øystein (2012). A physical interpretation of Hubble's law and the cosmological redshift from the perspective of a static observer. General Relativity and Gravitation.  ISSN 0001-7701.  44(10), s 2603- 2610 . doi: 10.1007/s10714-012-1417-5 Fulltekst i vitenarkiv.
• Gjerløw, Eirik & Elgarøy, Øystein (2011). Are all modes created equal? An analysis of the WMAP 5-and 7-year data without inflationary prejudice. Physical Review D. Particles and fields.  ISSN 0556-2821.  83(6) . doi: 10.1103/PhysRevD.83.067301
• Kristiansen, Jostein Riiser & Elgarøy, Øystein (2011). Reactor sterile neutrinos, dark energy, and the age of the universe. Astronomy and Astrophysics.  ISSN 0004-6361.  532 . doi: 10.1051/0004-6361/201117025
• Groeneboom, Nicolaas Ervik & Elgarøy, Øystein (2008). Detection of trans-Planckian effects in the cosmic microwave background. Physical Review D. Particles and fields.  ISSN 0556-2821.  77 . doi: 10.1103/PhysRevD.77.043522
• Kiakotou, A; Elgarøy, Øystein & Lahav, O (2008). Neutrino mass, dark energy, and the linear growth factor. Physical Review D. Particles and fields.  ISSN 0556-2821.  77 . doi: 10.1103/PhysRevD.77.063005
• Kristiansen, Jostein Riiser & Elgarøy, Øystein (2008). Cosmological implications of the KATRIN experiment. Journal of Cosmology and Astroparticle Physics.  ISSN 1475-7516. . doi: 10.1088/1475-7516/2008/01/007
• Elgarøy, Øystein (2007). Upper limits on neutrino masses from cosmology. Nuclear physics B, Proceedings supplements.  ISSN 0920-5632.  168, s 51- 53 . doi: doi:10.1016/j.nuclphysbps.2007.02.005
• Elgarøy, Øystein & Multamäki, Tuomas (2007). On using the cosmic microwave background shift parameter in tests of models of dark energy. Astronomy and Astrophysics.  ISSN 0004-6361.  471, s 65- 70 . doi: 10.1051/0004-6361:20077292
• Grøn, Øyvind; Elgaroy, O & Elgarøy, Øystein (2007). Is space expanding in the Friedmann universe models?. American Journal of Physics.  ISSN 0002-9505.  75 . doi: 10.1119/1.2360990
• Grøn, Øyvind & Elgarøy, Øystein (2007). Is space expanding in the Friedmann universe models. American Journal of Physics.  ISSN 0002-9505.  75(2), s 151- 157
• Kristiansen, Jostein Riiser; Elgarøy, Øystein & Dahle, Håkon (2007). Using the cluster mass function from weak lensing to constrain neutrino masses. Physical Review D. Particles and fields.  ISSN 0556-2821.  75 . doi: 10.1103/PhysRevD.75.083510
• Elgarøy, Øystein & Multamäki, T. (2006). Bayesian analysis of Friedmannless cosmologies. Journal of Cosmology and Astroparticle Physics.  ISSN 1475-7516.  09(002) . doi: 10.1088/1475-7516/2006/09/00
• Amarzguioui, Morad; Elgarøy, Øystein; Mota, David Fonseca & Multamaki, T (2006). Cosmological constraints on f(R) gravity theories within the Palatini approach. Astronomy and Astrophysics.  ISSN 0004-6361.  454, s 707- 714 . doi: 10.1051/0004-6361:20064994
• Elgarøy, Øystein & Lahav, Ofer (2006). Sub-eV upper limits on neutrino masses from cosmology. Physica Scripta.  ISSN 0031-8949.  127, s 105- 106
• Kristiansen, Jostein Riiser; Eriksen, Hans Kristian Kamfjord & Elgarøy, Øystein (2006). Revised WMAP constraints on neutrino masses and other extensions of the minimal Lambda CDM model. Physical Review D. Particles and fields.  ISSN 0556-2821.  74, s 123005
• Elgarøy, Øystein; Mota, David Fonseca & Multamäki, T. (2005). Loitering universe models in light of the CMB. Physical Review D. Particles and fields.  ISSN 0556-2821.  71
• Amarzguioui, Morad; Elgarøy, Øystein & Multamäki, T. (2005). Combined constraints on Cardassian models from supernovae, cosmic microwave background and large scale structure observations. Journal of Cosmology and Astroparticle Physics.  ISSN 1475-7516.  01, s 008
• Elgarøy, Øystein & Lahav, Ofer (2005). Neutrino masses from cosmological probes. New Journal of Physics.  ISSN 1367-2630.  7, s 61
• Elgarøy, Øystein & Multamäki, T. (2005). Cosmic acceleration and extra dimensions: constraints on modifications of the Friedmann equation. Monthly notices of the Royal Astronomical Society.  ISSN 0035-8711.  356, s 475- 479
• Evans, A. K. D.; Wehus, I. K.; Grøn, Øyvind & Elgarøy, Øystein (2005). Geometrical constraints on dark energy. Astronomy and Astrophysics.  ISSN 0004-6361.  430, s 399- 410
• Lahav, O & Elgarøy, Øystein (2005). Weighing neutrinos with large-scale structure. Nuclear physics B, Proceedings supplements.  ISSN 0920-5632.  143, s 439- 446
• Multamaki, T & Elgarøy, Øystein (2004). The Integrated Sachs-Wolfe effect as a probe of non-standard cosmological evolution. Astronomy and Astrophysics.  ISSN 0004-6361.  423, s 811- 819
• Ouyed, Rachid; Elgarøy, Øystein; Dahle, Håkon & Keranen, Petteri (2004). Meissner Effect and Vortex Dynamics in Quark Stars -- A Model for Soft Gamma-Ray Repeaters. Astronomy and Astrophysics.  ISSN 0004-6361.  420, s 1025- 1032 Vis sammendrag

  We present a new model for soft gamma-ray repeaters based on a quark star born with temperatures above the critical value (T_c) for the onset of the color-flavor locked superconductivity. The quark star then quickly cools below T_c, expelling a fraction of the surface magnetic field via the Meissner effect. We show that if a small fraction (\leq 10%) of the surface magnetic field (10^14 - 10^15 G) is expelled, it quickly decays via magnetic reconnection and heats up the quark star surface to temperatures > 10^9 K. Created (e+,e-) pairs annihilate into gamma rays emitted in a giant burst (the first burst in our model), with a luminosity of ~10^45 ergs s^-1. Subsequent bursts result from the restructuring of the surface magnetic field following the formation and relaxation of a vortex lattice which confines the internal magnetic field. During this phase, energy is sporadically released as a consequence of magnetic reconnection events in the entangled surface magnetic field as it evolves into a smooth, more stable, configuration. The star eventually enters a quiescent phase in which energy is continuously supplied by vortex annihilation at the surface. As the star spins down, the outermost vortex lines will be pushed to the surface where they annihilate and release their confined magnetic field. We show that the corresponding luminosity is L_v ~ 10^36 ergs s^-1 for a typical soft gamma-ray repeater spinning with a period of 8s and a surface magnetic field not exceeding 10^15 G. Our model can be applied to any situation where a T > T_c quark star is generated. We discuss the connection between anomalous X-ray pulsars and soft gamma-ray repeaters in the context of our model.

• Elgarøy, Øystein & Blasio, Fabio V. de (2001). Superfluid vortices in neutron stars. Astronomy and Astrophysics.  ISSN 0004-6361.  370, s 939- 950
• Elgarøy, Øystein; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (2001). Pairing correlations in nuclear systems, from infinite nuclear matter to finite nuclei. International journal of modern physics B.  ISSN 0217-9792.  15, s 1501- 1509
• Blasio, Fabio V. de & Elgarøy, Øystein (1999). Microscopic structure of a vortex line in superfluid neutron star matter. Physical Review Letters.  ISSN 0031-9007.  82(9), s 1815- 1818 Vis sammendrag

  The microscopic structure of an isolated vortex line in superfluid neutron star matter is studied by solving the Bogoliubov-De Gennes equations. Our study, which is a starting point for the microscopic, quantum-mechanical calculation of pinning forces in neutron stars, shows that the size of the vortex core varies differently with the density and pairing potential than that assumed in earlier calculations of vortex pinning in neutron star crusts.

• Elgarøy, Øystein; Engvold, Oddbjørn & Lund, N. (1999). The Wilson-Bappu effect of the MgIIk line - dependence on stellar temperature, activity and metallicity. Astronomy and Astrophysics.  ISSN 0004-6361.  343, s 222- 228
• Elgarøy, Øystein & Pethick, Christopher (1999). Absence of fragmentation of the condensate in a model for bosons in a trap. Physical Review A. Atomic, Molecular, and Optical Physics.  ISSN 1050-2947.  59(2), s 1711- 1714 Vis sammendrag

  Possible fragmentation of a Bose-Einstein condensate with negative scattering length is investigated using a simple two-level model. Our results indicate that fragmentation does not take place for values of the coupling for which the system is metastable. We also comment on the possibility of realizing a fragmented condensate in trapping potentials other than an harmonic one.

• Baldo, Marcello; Elgarøy, Øystein; Engvik, Lars; Hjorth-Jensen, Morten & Schulze, Hans-Josef (1998). Modern nucleon-nucleon potentials and 3P<SUB>2</SUB>-3F<SUB>2</SUB> pairing in neutron matter. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  58, s 1921- 1928
• Elgarøy, Øystein; Engvik, Lars; Hjorth-Jensen, Morten & Osnes, Eivind (1998). Minimal relativity and <SUP>3</SUP>S<SUB>1</SUB>-<SUP>3</SUP>D<SUB>1</SUB> pairing in symmetric nuclear matter. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  57, s 1069- 1072
• Elgarøy, Øystein & Hjorth-Jensen, Morten (1998). Nucleon-nucleon phase shifts and pairing in infinite matter. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  57, s 1174- 1177
• Blasio, Fabio V. de; Hjorth-Jensen, Morten; Elgarøy, Øystein; Engvik, Lars; Lazzari, Gianluca; Baldo, Marcello & Schulze, Hans-Josef (1997). Coherence lengths of neutron superfluids. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  56, s 2332- 2335
• Elgarøy, Øystein; Engvik, Lars; Hjorth-Jensen, Morten & Osnes, Eivind (1996). Model-space approach to ¹S₀ neutron and proton pairing in neutron star matter with the Bonn meson-exchange potentials. Nuclear Physics A.  ISSN 0375-9474.  604, s 466- 490
• Elgarøy, Øystein; Engvik, Lars; Hjorth-Jensen, Morten & Osnes, Eivind (1996). Superfluidity in _b-stable neutron star matter. Physical Review Letters.  ISSN 0031-9007.  77, s 1428- 1431
• Elgarøy, Øystein; Engvik, Lars; Hjorth-Jensen, Morten & Osnes, Eivind (1996). Triplet pairing of neutrons in _b-stable neutron star matter. Nuclear Physics A.  ISSN 0375-9474.  607, s 425- 441
• Elgarøy, Øystein; Engvik, Lars; Osnes, Eivind; Blasio, Fabio V. de; Lazzari, Gianluca & Hjorth-Jensen, Morten (1996). Emissivities of neutrinos in neutron stars. Physical Review Letters.  ISSN 0031-9007.  76, s 1994- 1997
• Elgarøy, Øystein; Engvik, Lars; Osnes, Eivind; Blasio, Fabio V. de; Lazzari, Gianluca & Hjorth-Jensen, Morten (1996). Superfluidity and neutron star crust matter. Physical Review D. Particles and fields.  ISSN 0556-2821.  54, s 1848- 1851

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• Elgarøy, Øystein (2015). Hvordan finner man mørk energi?, I: Jostein Riiser Kristiansen; Anna Kathinka Dalland Evans; Henrik Svensen; Bjørn Hallvard Samset & Hanne Sigrun Byhring (red.),  Stjerneklart – siste nytt fra verdensrommet.  Spartacus.  ISBN 9788243009738.  Kapittel 29.  s 166 - 177
• Elgarøy, Øystein (2015). Inflasjon: Da universet løp løpsk, I: Jostein Riiser Kristiansen; Anna Kathinka Dalland Evans; Henrik Svensen; Bjørn Hallvard Samset & Hanne Sigrun Byhring (red.),  Stjerneklart – siste nytt fra verdensrommet.  Spartacus.  ISBN 9788243009738.  Kapittel 10.  s 61 - 71
• Elgarøy, Øystein (2006). Upper limits on neutrino masses from cosmology.
• Elgarøy, Øystein & Lahav, Ofer (2006). Sub-eV upper limits on neutrino masses from cosmology.
• Elgarøy, Øystein (1999). Superfluidity in Infinite Nuclear Systems.
• Elgarøy, Øystein; Engeland, Torgeir; Hjorth-Jensen, Morten & Osnes, Eivind (1999). Pairing correlations, from finite nuclei to infinite matter.
• Elgarøy, Øystein & Lemstad, Frank (1999). Christopher Hansteen og jordmagnetismen. Astronomisk tidsskrift.  ISSN 0004-6345.  32(3), s 12- 17
• Vidanya, Isaac; Polls, Artur; Ramos, Angels; Elgarøy, Øystein; Engvik, Lars & Hjorth-Jensen, Morten (1999). Properties of _b stable neutron star matter with hyperons.
• Elgarøy, Øystein & Hjorth-Jensen, Morten (1998). Properties of Pairing Correlations in Infinite Nuclear Matter.

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