Browsing by Author "Haataja, Hanna"

In this thesis we introduce the Coleman-Weinberg mechanism through sample calculations. We calculate the effective potential in the massless scalar theory and massless quantum electrodynamics. After sample calculations, we walk through simple model in which the scalar particle, that breaks the scale invariance, resides at the hidden sector. Before we go into calculations we introduce basic concepts of the quantum field theory. In that context we discuss interaction of the fields and the Feynman rules for the Feynman diagrams. Afterwards we introduce the thermal field theory and calculate the effective potential in two cases, massive scalar theory and the Standard Model without fermions. We introduce the procedure how to calculate the effective potential, which contains ring diagram contributions. Motivation for this is knowledge of that sometimes the spontaneously broken symmetries are restored in the high temperature regime. If the phase transition between broken-symmetry and full-symmetry phase is first order phase transition baryogenesis can happen. Using the methods introduced in this thesis the Standard Model extensions that contain hidden sectors can be analyzed.