|Ph.D Thesis||Department of Physics|
|Supervisor:||Assoc. Prof. Shadmi Yael|
|Full Thesis text|
The hierarchy between the electro-weak and Planck scale, and the fine-tuning needed to maintain this hierarchy are considered to be the main problem of the Standard Model. Both spontaneously broken supersymmetry and extra-dimensional models provide viable solutions to these problems. In this thesis we study various topics related to supersymmetry breaking and extra-dimensional models.
The first two chapters of the thesis deal with supersymmetry breaking. In the first chapter we study the possibility that supersymmetry breaking originates from Lorentz violation in the hidden sector. We show that in this case the soft masses are related to the Lorentz violation in the visible sector. The current bounds on Lorentz violation imply that the soft masses are tiny. In the process we review one of the strongest bounds on Lorentz violation and show that it does not apply in a very wide range of models of Lorentz violation.
In the second chapter we examine the hypothesis of a meta-stable supersymmetry breaking vacuum in SQCD with number of flavors equals to the number of colors. We show that this minimum does not exist in the calculable regime of a certain deformation with gauge singlets. We claim that no additional evidence can be gained by deforming the theory. We also discuss the consequences of the singlets in the "Pentagon" model.
The last three chapters concentrate on different aspects of the Randall-Sundrum model. In the third chapter we use deconstruction to study the running of the gauge couplings in this model. We derive the expression for the gauge coupling at low energies for arbitrary lattice graining. We show that aside from a leading logarithmic term there is a small linear dependence on the cut off. We also derive the gauge boson profile at intermediate energies, perturbing around the coarse lattice limit.
In the last two chapters we study the supersymmetric Randall-Sundrum model with mistuned brane tensions. In this scenario supersymmetry can be spontaneously broken by boundary conditions. We study moduli stabilization in this scenario and the possibility of uplifting the cosmological constant by quantum corrections.