Browsing Institutt for teoretisk astrofysikk by Title
Now showing items 180-199 of 600
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(Master thesis / Masteroppgave, 2019)
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(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2012)We consider issues related to the conformal mapping between the Einstein and Jordan frames in f(R) cosmology. We consider the impact of the conformal transformation on the gauge of a perturbed system and show that unless ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)In the first-order formalism of gravitational theories, the spacetime connection is considered as an independent variable to vary together with the metric. However, the metric still generates its Levi-Civita connection ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)© 2017. The American Astronomical Society. All rights reserved.
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(Master thesis / Masteroppgave, 2011)There have been many reports on anomalies in the CMB from different research groups. In this work statistical tests using the gradients of the CMB temperature, applied to the seven year WMAP data, have been investigated. ...
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(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)During the epoch of reionization, neutral gas in the early Universe was ionized by hard ultraviolet radiation emitted by young stars in the first galaxies. To do so, ionizing ultraviolet photons must escape from the host ...
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(Master thesis / Hovedoppgave, 2002)It is believed that the Broad Emission Line Region of Quasars consists of discrete clouds. Due to the suspected small size of a cloud, the radiation from clouds may be strongly amplified by gravitational microlensing. It ...
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(Master thesis / Masteroppgave, 2013)The gravitational redshift in clusters of galaxies can be measured to probe gravity as was first done by Wojtak et al. (2011). Using N -body simulations we are able to analyze the gravitational redshift profiles for the ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)Aims: We investigate the gravitational redshift in clusters of galaxies in the symmetron and Hu-Sawicky f(R) models. The characteristic feature of both models is the screening mechanism that hides the fifth force in dense ...
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(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2019)The evolution of the virial overdensity Δvir for ΛCDM and seven dynamical dark-energy models is investigated in the extended spherical collapse model (SCM). Here the virialization process is naturally achieved by introducing ...
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(Master thesis / Masteroppgave, 2013)Modified gravity theories are a popular research field in the hope that they could explain some of the unanswered questions in cosmology, for example how the universe starts, evolves and ends. One way to test proposed ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)Screened modified gravity predicts potentially large signatures in the peculiar velocity field that makes it an interesting probe to test gravity on cosmological scales. We investigate the signatures induced by the Symmetron ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)The heating of the Sun's chromosphere remains poorly understood. While progress has been made on understanding what drives the quiet-Sun internetwork chromosphere, chromospheric heating in strong magnetic field regions ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)We use coordinated observations with the Interface Region Imaging Spectrograph (IRIS) and the Swedish 1 m Solar Telescope to identify the disk counterpart of type II spicules in upper-chromospheric and transition region ...
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(Master thesis / Masteroppgave, 2010)
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)We studied the physical parameters of the penumbra in a large and fully developed sunspot, one of the largest over the last two solar cycles, by using full-Stokes measurements taken at the photospheric Fe i 617.3 nm and ...
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(Doctoral thesis / Doktoravhandling, 2007)Doktorgradsavhandlingen beskriver et programvarebibliotek utviklet av Øystein Olsen ved Institutt for teoretisk astrofysikk. Programvaren har blitt brukt til å finne regioner med stabile og ustabile baner rundt asteroider ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)We present high-resolution, high-cadence observations of six, fine-scale, on-disk jet-like events observed by the High-resolution Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We combine the Hi-C 2.1 ...
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(Master thesis / Masteroppgave, 2011)Spicules are relatively small, narrow and elongated structures that stick out above the edge of the solar disk. They are very dynamic and appear as jets that shoot out into the outer solar atmosphere. Up until recently, ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)We characterize waves in small magnetic elements and investigate their propagation in the lower solar atmosphere from observations at high spatial and temporal resolution. We use the wavelet transform to analyze oscillations ...