Browsing Institutt for teoretisk astrofysikk by Issue Date
Now showing items 41-60 of 1306
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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, 2011)Oscillations with periods on the order of 5–10 min have been observed by instrumented spacecrafts in the Earth's magnetosphere. These oscillations often follow sudden impacts related to coronal mass ejections. It is ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2011)We introduce the N-body simulation technique to follow structure formation in linear and nonlinear regimes for the extended quintessence models (scalar-tensor theories in which the scalar field has a self-interaction ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2011)We investigate whether there is any cosmological evidence for a scalar field with a mass and coupling to matter which change accordingly to the properties of the astrophysical system it “lives in,” without directly focusing ...
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(Master thesis / Masteroppgave, 2011)The existence of dark matter is a well established fact both due to galaxy rotation curves and also due to the CMB temperature anisotropies and the matter power spectra. According to the $\Lambda$CDM model, the so called ...
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(Master thesis / Masteroppgave, 2012)The Q/U-Imaging ExperimenT (QUIET) is a ground-based coherent polarimeter experiment, primarily targeting the detection of low-l B-mode polarization in the CMB. Such modes are a signature of primordial tensor perturbations, ...
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(Master thesis / Masteroppgave, 2012)The solar corona has a temperature of order 1 MK, which is almost 200 times the temperature of the underlying surface. This fact has puzzled solar physicists for more than six decades. As of today, most solar physicists ...
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(Master thesis / Masteroppgave, 2012)Inflation is a much discussed topic within the field of cosmology; it represents a time in the history of the Universe where a very rapid, exponential expansion was taking place. This expansion is needed in order for the ...
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(Master thesis / Masteroppgave, 2012)The inverse-C shape of the bisector from the chromospheric Ca triplet spectral lines is a little understood phenomena. This spectral signature can give valuble information about the chromosphere, which is the least understood ...
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(Doctoral thesis / Doktoravhandling, 2012)
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(Doctoral thesis / Doktoravhandling, 2012)
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)Scalar fields, strongly coupled to matter, can be present in nature and still be invisible to local experiments if they are subject to a screening mechanism. The symmetron is one such mechanism that relies on restoration ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)It is shown that extensions to general relativity, which introduce a strongly coupled scalar field, can be viable if the interaction has a nonconformal form. Such disformal coupling depends upon the gradients of the scalar ...
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(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 ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)Recently, a modified theory of gravity was presented, which consists of the superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed à la Palatini. The theory possesses extremely interesting ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)The bimetric variational principle is a subtle reinterpretation of general relativity that assumes the spacetime connection to be generated by an independent metric. Unlike the so-called Palatini formalism that promotes ...
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(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 ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)A completely new mechanism to generate the observed amount of large-scale cosmological magnetic fields is introduced in the context of three-form inflation. The amplification of the fields occurs via fourth order dynamics ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)We present a novel approach to modified theories of gravity which consists of adding to the Einstein-Hilbert Lagrangian an f(R) term constructed à la Palatini. Using the respective dynamically equivalent scalar-tensor ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)Recently, a supersymmetric model of dark energy coupled to cold dark matter, the supersymmetron, has been proposed. In the absence of cold dark matter, the supersymmetron field converges to a supersymmetric minimum with a ...