We propose a new method for detecting exoplanets using gravita-tional lensing. The hypothesis is that the lensing caused by an exo-planet could distort the structures of a radio background, for instancea H II region. It cannot be done with todays telescope but with thesecond incarnation of the Square Kilometer Array (SKA), currently inits design phase we deem it possible. In order to test this hypothesis weconstructed a simulation that creates a simple background structurewith variable scale and then produces simulated images such as theones achievable with the SKA. We produce positive result with a clearsignature of the planet with certain background scales and suggestfurther investigation into this method of detecting exoplanets.

No description available.

No description available.

No description available.

<p>It is an intriguing possibility that our world may consist of more than three spatial dimensions, compactified on such a small scale that they so far have escaped detection. In this thesis, a particular realization of this idea -- the scenario of so-called 'universal extra dimensions' (UED) -- is studied in some detail, with a focus on cosmological consequences and appplications.</p><p>The first part investigates whether the size of homogeneous extra dimensions can be stabilized on cosmological time scales. This is necessary in order not to violate the stringent observational bounds on a possible variation of the fundamental constants of nature.</p><p>An important aspect of the UED model is that it can provide a natural explanation for the mysterious dark matter, which contributes nearly thirty times as much as luminous matter like stars, galaxies etc. to the total energy content of the universe. In the second part of this thesis, the observational prospects for such a dark matter candidate are examined. In particular, it is shown how dark matter annihilations taking place in the Milky Way could give rise to exotic contributions to the cosmic ray spectrum in photons and antiprotons, leading to distinct experimental signatures to look for.</p><p>This includes a comparison with similar effects from other dark matter candidates, most notably the neutralino, which appears in supersymmetric extensions of the standard model of particle physics.</p>

It is an intriguing possibility that our world may consist of more than three spatial dimensions, compactified on such a small scale that they so far have escaped detection. In this thesis, a particular realization of this idea -- the scenario of so-called 'universal extra dimensions' (UED) -- is studied in some detail, with a focus on cosmological consequences and appplications. The first part investigates whether the size of homogeneous extra dimensions can be stabilized on cosmological time scales. This is necessary in order not to violate the stringent observational bounds on a possible variation of the fundamental constants of nature. An important aspect of the UED model is that it can provide a natural explanation for the mysterious dark matter, which contributes nearly thirty times as much as luminous matter like stars, galaxies etc. to the total energy content of the universe. In the second part of this thesis, the observational prospects for such a dark matter candidate are examined. In particular, it is shown how dark matter annihilations taking place in the Milky Way could give rise to exotic contributions to the cosmic ray spectrum in photons and antiprotons, leading to distinct experimental signatures to look for. This includes a comparison with similar effects from other dark matter candidates, most notably the neutralino, which appears in supersymmetric extensions of the standard model of particle physics.

In this thesis we consider perturbations of a perfect fluid on locally rotationally symmetrical (LRS) class II cosmological backgrounds, with a nonvanishing vorticity of the fluid on the perturbed model. The method used is based on the 1+1+2 covariant decomposition of spacetime, motivated by the assumption of anisotropic expansion, followed by a harmonic decomposition of all gauge invariant quantities. All perturbed quantities can be solved for in terms of the time evolution equations of eight harmonic coefficients. This set of eight harmonic coefficients decouple into an even and odd sector, containing five and three variables respectively, where the vorticity is represented as one variable in each sector. We find that the time evolution of the vorticity completely decouples from the other perturbed variables, and can be solved exactly by assuming a linear equation of state. The evolution of the remaining perturbed variables are examined in the geometrical optics approximation, and compared to research looking at the case when the vorticity vanishes on the perturbed model. The results turn out to be the same, except for a source term containing the odd parity of the vorticity in the evolution of the density, which act as a source term for the shear waves. The four remaining variables will represent damped, source free gravitational waves.

The very-high-energy gamma-ray emission of the hard spectrum BL Lac source 1H1914-194 has been studied with Fermi-LAT data covering a nearly ten-year period between August 2008 until March 2018 in the energy range of 300 MeV to 870 GeV. The mean flux has been determined as 8.4 x 10-9±3.5 x 10-10 photon cm-2 s-1. The data processing has been done with the Enrico software using the Fermi Science Tools (v10r0p5) and the Pass 8 version of the data, performing binned analysis in order to handle the long integration time. The lightcurve shows that the source has to be considered as variable in the given time period for a three-month binning. It gives furthermore evidence for at least one quiet and active period lasting slightly over 1.5 years each. Even these shorter periods show a weak variability. The significance of the source has been determined as σ = 57.5 for a one-year period. The spectral analysis of three different time periods have been fitted by PowerLaw2, LogParabola and PLExpCutoff functions resulting in LogParabola being slightly favored in most of the cases. However, the test statistic are not showing enough significance that may lead to an unambiguous preference. The data from the analysis has been implemented in a multiwavelength view of the source, showing that the analysis is in agreement with the data coming from the Fermi catalogs. The overall emission of 1H1914-194 has been modelled with theoretical frameworks based on a one-zone Synchrotron Self Compton (SSC) model providing an acceptable description of the SED.

No description available.

No description available.