Non-perturbative phenomena and the electroweak phase transition

Abstract

The aim of this thesis is to investigate various non-perturbative phenomena within and beyond the standard model and their implications on the electroweak phase transition. The perturbative spectrum of the standard model is well-known and its properties have been measured to great precision. However, the same cannot be said for the non-perturbative spectrum. We first show the existence of electroweak monopoles with finite energy in a Born-Infeld extension of the standard model. We calculate this mass and discuss experimental constraints from light by light scattering and vector boson scattering processes. We also show that these monopoles are a source of B+L - and CP-violation which could potentially provide a novel method of detecting them. We then propose a new mechanism of baryogenesis through B+L - and CP-violating monopole-antimonopole annihilation processes. The phenomenon of scale invariance is an elegant solution to the hierarchy problem. We consider a model in which the standard model is a low energy effective theory with a UV completion that exhibits scale invariance. We compute the thermal effective potential for this model and show that the electroweak phase transition is dramatically different in this theory, only occurring after the QCD chiral phase transition. We also discuss phenomenological implications of this scenario. Finally, we inspect the role of gravity in quantum electrodynamics. We show that quantum gravity effects driven by electrically charged gravitational instantons give rise to a topologically non-trivial vacuum structure resulting in important phenomenological consequences like the violation of CP and the quantisation of electric charge. These models demonstrate that the detailed study of non-perturbative phenomena can yield interesting and significant results and can be the key to answering the unanswered questions in particle physics and cosmology.