Browsing Institutt for teoretisk astrofysikk by Title
Now showing items 5473 of 516

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)We report on the discovery of periodic coronal rain in an offlimb sequence of Solar Dynamics Observatory/Atmospheric Imaging Assembly images. The showers are cospatial and in phase with periodic (6.6 hr) intensity ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2012)A completely new mechanism to generate the observed amount of largescale cosmological magnetic fields is introduced in the context of threeform inflation. The amplification of the fields occurs via fourth order dynamics ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)We test anisotropic dark energy models with the 7year WMAP temperature observation data. In the presence of imperfect sources, largescale gradients or anisotropies in the dark energy mean that the CMB sky will be distorted ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)Extending general relativity by adding extra degrees of freedom is a popular approach for explaining the accelerated expansion of the Universe and to build high energy completions of the theory of gravity. The presence of ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)We measure the cosmological bias factor of damped Ly α absorbers (DLAs) from their crosscorrelation with the Ly α forest absorption, as a function of the DLA metal strength, defined from an average of equivalent widths of ...

(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 ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)We propose an efficient Bayesian Markov chain Monte Carlo (MCMC) algorithm for estimating cosmological parameters from cosmic microwave background (CMB) data without the use of likelihood approximations. It builds on a ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)Cosmological perturbations due to statistical thermal fluctuations in a single fluid characterized by an arbitrary equation of state are computed. Formulas to predict the scalar and tensor perturbation spectra and ...

(Doctoral thesis / Doktoravhandling, 2013)

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2014)In the context of scalar tensor theories for gravity, there is a universally adopted hypothesis when running Nbody simulations that time derivatives in the equation of motion for the scalar field are negligible. In this ...

(Master thesis / Masteroppgave, 2015)In this thesis, we investigate statistical properties of the redshift zero matter distribution in disformal gravity through Nbody simulations. The disformal model studied here is a conformally coupled field in a symmetron ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)Aims: We study the effects of letting dark matter and gas in the Universe couple to the scalar field of the symmetron model, a modified gravity theory, with varying coupling strength. We also search for a way to distinguish ...

(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 ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2018)Euclid is a European Space Agency mediumclass mission selected for launch in 2020 within the cosmic vision 2015–2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. ...

(Master thesis / Masteroppgave, 2014)In this thesis we investigate a dynamical cosmological constant called the quintessence. Quintessence is a scalar field varying in both space and time following a chosen potential. To explain the coincidence problem, e.g. ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)We study the cosmological evolution for a universe in the presence of a continuous tower of massive scalar fields which can drive the current phase of accelerated expansion of the universe and, in addition, can contribute ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2008)Conditional sampling methods are generalized by applying a matchedfilter on the reference signal. This generalized method is illustrated by data obtained in a magnetized toroidal plasma without rotational transform. By ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)The production of scienceready data from major solar telescopes requires expertise beyond that of the typical observer. This is a consequence of the increasing complexity of instruments and observing sequences, which ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)Lineintensity mapping is an emerging field of observational work, with strong potential to fit into a larger effort to probe largescale structure and smallscale astrophysical phenomena using multiple complementary ...

(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2013)Observations of transition region emission lines reveal the presence of redshifts in lines formed from the top of the chromosphere up to temperatures of about 2.5 × 105 K and blueshifts for temperatures above that. However, ...