Browsing Institutt for teoretisk astrofysikk by Title
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(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, 2019)Highenergy particles enter the solar atmosphere from Galactic or solar coronal sources, and produce ‘albedo’ emission from the quiet Sun that is now observable across a wide range of photon energies. The interaction of ...

(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, 2019)Modified gravity (MG) theories aim to reproduce the observed acceleration of the Universe by reducing the dark sector while simultaneously recovering General Relativity (GR) within dense environments. Void studies appear ...

(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, 2019)The dominant feedback mechanism in lowmass haloes is usually assumed to take the form of massive stars exploding as supernovae (SNe). We perform very high resolution cosmological zoomin simulations of five dwarf galaxies ...

(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. ...

(Doctoral thesis / Doktoravhandling, 2020)The standard model of cosmology has been quite successful in describing how baryonic matter and dark matter cluster by means of gravity, forming the structures we can see today while looking at the sky, and it can reproduce ...

(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 ...