Electroweak Phase Transitions
Abstract
An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles, and completes at a temperature where the order parameter, <phi>_ {T}, is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially sensitive function of <phi> _{T}. In very minimal extensions of the standard model it is quite easy to increase <phi>_{T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal extensions of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value <phi> = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state <phi> = 246 GeV unstable. The requirement that the state <phi> = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field. Semiclassical reasoning suggests that, when a particle receives a contribution to its mass from the vacuum expectation value of a scalar, under certain conditions, the ground state of particle number one contains a 'dimple' or shallow scalar field condensate around the particle. We argue that this is not the case. A careful analysis, taking into account quantum mechanics, shows that the semiclassical approximation is a poor one. We find that there are no energetically favored oneparticle dimple solutions for perturbative couplings.
 Publication:

Ph.D. Thesis
 Pub Date:
 1991
 Bibcode:
 1991PhDT........43A
 Keywords:

 STANDARD MODEL;
 HIGGS BOSON;
 FIELD THEORY;
 Physics: Elementary Particles and High Energy, Physics: Astronomy and Astrophysics