Filtyp
Gravitational encounters between a single star and a binary system can frequently occur in the cores of dense stellar systems like globular clusters. These three-body scattering encounters can lead to a variety of outcomes since the energy of the binary components can be exchanged with the interacting single star. The outcome of these interactions strongly depend on the initial conditions of the i
Protoplanetary discs surround young stars for the first few million years after their formation and they are the birthplaces of planetary systems. The thermal structure of the discs is regulated by their dust content and the opacity that it provides. The aim of this project is to investigate the effect grain growth has on the structure of the protoplanetary discs. Hydrodynamical simulations have b
Star clusters can harbour many exotic objects, including black holes (BHs), X-ray binaries and blue straggler stars. In dense stellar environments like globular clusters (GCs), two-body relaxation drives their dynamical evolution, where gravitational interactions between stars strive to equalize their kinetic energy in the cluster. Theoretical studies have indicated that some of these clusters can
This is a bachelor thesis bent on introducing the field of exoplanet research. It primarily includes descriptions of the various detection methods, with some detail into how the methods yield parameter estimates by means of least-squares algorithms. The feasibility of combining state-of-the-art astrometric capabilities of Gaia and radial velocity measurements from ground level is briefly discussed
Imaging of stellar surfaces in visible wavelengths is one of the current frontiers in astronomy. With a few exceptions, stars can not be seen in visible light as anything but point objects with current technology. Being able to properly image stars would open up the door to a vast field of new discoveries, permitting direct studies of phenomena such as rotationally deformed stars, circumstellar di
The black hole information paradox is of central importance in the study of quantum gravity. The paradox states that quantum fields surrounding a black hole behave in ways that run into conflict with the unitarity of quantum mechanical time evolution. In the course of the past two years, new theoretical discoveries have made progress towards the paradox’s resolution, suggesting that unitarity can
We present a generalisation of the flavour-ordering method applied to the chiral nonlinear sigma model with any number of flavours. We use an extended Lagrangian with terms containing any number of derivatives, organised in a power-counting hierarchy. The method allows diagrammatic computations at tree-level with any number of legs at any order in the power-counting. Using an automated implementat
In this thesis, we consider a 2-Higgs-doublet model with a gauged Froggatt-Nielsen mechanism as an extension of the standard model. We assume that (i) the theory at the electroweak scale is the low energy limit of a theory defined at a scale $\Lambda_{FN}$ (ii) the Yukawa couplings at $\Lambda_{FN}$ are generated by the Froggatt-Nielsen mechanism. The first assumption is enforced by requiring that
The possibility to have a strongly first order electroweak phase transition, which is one of the Sakharov conditions for electroweak baryogenesis together with $\mathcal{CP}$ violation and baryon number violation, in general Two-Higgs-Doublet Models (2HDMs) is here investigated. Different kinds of $\mathbb{Z}_{2}$ breaking beyond standard assumptions are studied, in particular by allowing it to be
In this thesis, a holographic model for quantum chromodynamics (QCD) is used to estimate the electromagnetic contribution to the kaon mass difference. The principal ideas of the model are inspired by the AdS/CFT correspondence, which is believed to be exact. The calculation is first performed theoretically, highlighting the expansion of the result into a diagrammatic structure referred to as Witte
This thesis will investigate the possibility to have SU(2) gauge fields as the source to the Cosmic Inflation and/or to the Dark Energy. It will be explained that, under certain conditions, the Universe can be filled with vector fields without violating its isotropy. Those conditions are naturally fulfilled within the SU(2) gauge theory. Both Einstein's equations and the equations of motion
Chiral perturbation theory is an efficient effective theory to describe meson-meson scattering at low energy. An effective theory naturally introduces low energy constants and they are used, for example, to solve the ultraviolet divergences. The aim of this master thesis is to focus on meson-meson scattering to find some theoretical bounds on the coupling constants, based mainly on arguments from
One approach to understanding the observed hierarchy in quark masses is by using the Froggatt-Nielssen mechanism. In this model new exotic (and presumable yet undetected) particles are introduced. By forcing the particles of the Standard Model to interact with the postulated particles it is possible to create a mass suppression mechanism which can explain the observed quark mass relations. The me
The thesis treats the construction of a supersymmetric model, inspired by an E8 unfication scenario. Via the introduction of adjoint representation chiral superfields, in combination with the inclusion of a global generation symmetry, the Standard Model fermion candidates are protected from gaining any mass until electroweak symmetry breaking. In addition, an accidental global baryon symmetry proh
We review the factorization theorem for the production of a heavy color-neutral final state with a transverse momentum much smaller than its invariant mass in the framework of soft collinear effective field theory (SCET). This phase space region is plagued by large logarithms of widely separated scales, including large logarithms of rapidity ratios, that need to be resummed for sensible results. I
We have studied left-right-symmetric (LR) model building in two specific instances: the Minimal Left-Right-Symmetric Model (MLRM), with gauge group SU(3)_C × SU(2)_L × SU(2)_R × U(1)_{B-L} and parity as the LR symmetry; and a non-supersymmetric, trinified theory, with gauge structure SU(3)_L × SU(3)_R × SU(3)_C × Z_3 and an additional, novel, SU(3) family symmetry. For the MLRM, we have rederive
In this thesis we investigate the properties of a specific two Higgs Doublet Model (2HDM) that can be used to explain the data on B->Dtu and B->D*tu, which deviate from the Standard Model (SM) by 3.4 sigma. The 2HDM is the simplest extension of the Standard model scalar sector. Phenomenologically it is very rich with 4 new Higgs bosons: 2 neutral and an electromagnetic charged pair. The 2HDMs exhi
