Now showing items 703-722 of 735

  • Mouland, Maria (Master thesis / Masteroppgave, 2009)
    I have investigated the total energy of Friedmann-Robertson-Walker universes. This is an interesting issue, because if the energy of the universe turns out not to be conserved, it will be in conflict with our common ...
  • Eide, Marius Berge (Master thesis / Masteroppgave, 2015)
  • Biswas, T.; Gerwick, E.; Koivisto, Tomi Sebastian; Mazumdar, A. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
    We present the most general covariant ghost-free gravitational action in a Minkowski vacuum. Apart from the much studied f(R) models, this includes a large class of nonlocal actions with improved UV behavior, which ...
  • Christensen, Charlotte R.; Davé, Romeel; Brooks, Alyson M.; Quinn, Thomas; Shen, Sijing (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    We analyze the metal accumulation in dwarf and spiral galaxies by following the history of metal enrichment and outflows in a suite of 20 high-resolution simulated galaxies. These simulations agree with the observed stellar ...
  • Bratli, Eirik (Master thesis / Masteroppgave, 2020)
  • Groeneboom, Nicolaas Ervik (Master thesis / Masteroppgave, 2007)
  • Morton, Richard J.; Mooroogen, K; de Jorge Henriques, Vasco Manuel (Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)
    Sunspots have played a key role in aiding our understanding of magnetohydrodynamic (MHD) wave phenomena in the Sun’s atmosphere, and it is well known they demonstrate a number of wave phenomena associated with slow MHD ...
  • Jafarzadeh, Shahin; Solanki, S. K.; Gafeira, Ricardo; van Noort, M.; Barthol, P.; Blanco Rodriguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L; Hirzberger, J.; Knölker, M.; Orozco Suarez, D.; Riethmüller, T. L.; Schmidt, W. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    We present observations of transverse oscillations in slender Ca ii H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution seeing-free observations in ...
  • Antolin, Patrick; Schmit, D.; Pereira, Tiago Mendes Domingos; De Pontieu, Bart Walter; De Moortel, I. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    In addition to their jet-like dynamic behavior, spicules usually exhibit strong transverse speeds, multi-stranded structure, and heating from chromospheric to transition region temperatures. In this work we first analyze ...
  • Del Popolo, Antonino; Chan, Man Ho; Mota, David (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    We determine the relationship between the turnaround radius, Rt, and mass, Mt, in Λ CDM , and in dark energy scenarios, using an extended spherical collapse model taking into account the effects of shear and vorticity. We ...
  • Martinez-Sykora, Juan; De Pontieu, Bart Walter; Carlsson, Mats; Hansteen, Viggo; Nobrega-Siverio, Daniel; Gudiksen, Boris Vilhelm (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)
    We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ...
  • Mas Ribas, Lluis; Mauland-Hus, Renate (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
    Observational evidence revealing the main mechanisms that accelerate quasar outflows has proven difficult to obtain due to the complexity of the absorption features that this gas produces in the spectra of the emission ...
  • de Jorge Henriques, Vasco Manuel; Nelson, Chris J.; Rouppe van der Voort, Luc; Mathioudakis, Mihalis (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)
    Context. The chromosphere of the umbra of sunspots features an assortment of dynamic fine structures that are poorly understood and often studied separately. Small-scale umbral brightenings (SSUBs), umbral microjets, spikes ...
  • Allred, Joel C.; Kowalski, Adam F.; Carlsson, Mats (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    We present a unified computational framework that can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is ...
  • Brax, P; Davis, A.-C.; Li, Baojiu; Winther, Hans Arnold (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)
    We consider modified gravity models driven by a scalar field whose effects are screened in high density regions due to the presence of nonlinearities in its interaction potential and/or its coupling to matter. Our approach ...
  • Salzano, Vincenzo; Mota, David; Capoziello, S.; Napolitano, N. R. (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    Aims: We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron, and f(R)-gravity models, we studied a phenomenological ...
  • Gronke, Max Balthasar; Mota, David; Winther, Hans Arnold (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)
    Modified gravity models require a screening mechanism to be able to evade the stringent constraints from local gravity experiments and, at the same time, give rise to observable astrophysical and cosmological signatures. ...
  • Mason, Charlotte A.; Treu, Tommaso; Dijkstra, Mark; Mesinger, Andrei; Trenti, Michele; Pentericci, Laura; De Barros, Stephane; Vanzella, Eros (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    We present a new flexible Bayesian framework for directly inferring the fraction of neutral hydrogen in the intergalactic medium (IGM) during the Epoch of Reionization (EoR, z ~ 6–10) from detections and non-detections of ...
  • Eide, Marius Berge; Gronke, Max Balthasar; Dijkstra, Mark; Hayes, Matthew (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)
    Lyα is a powerful astrophysical probe. Not only is it ubiquitous at high redshifts, it is also a resonant line, making Lyα photons scatter. This scattering process depends on the physical conditions of the gas through which ...
  • Scullion, Eamon; Rouppe, Van Der Voort Luc; Wedemeyer-Böhm, Sven; Antolin, Patrick (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)
    New and advanced space-based observing facilities continue to lower the resolution limit and detect solar coronal loops in greater detail. We continue to discover even finer substructures within coronal loop cross-sections, ...