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The aim of this work is to determine whether any zero temperature features of the scalar potential strongly influence the finite temperature properties of the electroweak phase transition. In particular, we address whether one can get an arbitrarily strong phase transition from zero temperature effects. We investigate a variety of models of varying complexity. For the models we look into, we successfully determine that the vacuum energy difference at zero temperature has a direct influence on the critical temperature. This leads to arbitrarily strong phase transitions, subject to the caveat that sliding behaviour does not occur. What we call sliding behaviour is the scenario in which the broken vacuum destabilises under thermal corrections before reaching the critical temperature. The parameter subspace in which sliding behaviour does occur often leads to significantly weakened phase transitions. For a more detailed investigation of the phase transition one must look at the thermal decay of the false vacuum. Choosing a non-supersymmetric real singlet extension to the Standard Model, called the xSM, we detail by example how one can systematically investigate some non-trivial phase transition properties. The specific model we adopt is the Z2xSM which has a Z2 discrete symmetry imposed on the singlet as well as the Higgs field. We focus on the non-sliding parameter subspace, which has a minimal zero temperature parameter space of only three free parameters. For this setup, the depth of the potential at zero temperature has a one-to-one mapping with the strength of the phase transition at critical temperature so we can trivially choose the strength. This allows for a systematic approach to investigating very strong phase transitions and their connection to the amount of supercooling, latent heat, bubble nucleation rate, and a hydrodynamical friction parameter. We also trace out the parameter region in which runaway bubbles are expected and discuss the implications for gravitational wave production.

Thesis (Ph. D.)--University of Oregon, 2003. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 178-181). Also available for download via the World Wide Web; free to University of Oregon users.

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In this thesis we investigate the scattering of neutrinos and antineutrinos off free protons in the deep inelastic region via the neutral weak current. In the BEBC experiment, a hybrid detector consisting of a large liquid hydrogen bubble chamber and electronic counters for muon and hadron identification, has been exposed to the CERN wide band beam of neutrinos with energies up to 300 GeV. The detector provides the possibility to discriminate efficiently between hadron-induced and neutrino-induced muonless events. We are interested in the structure of the proton as it is resolved by the neutral carrier Zº of the electroweak force. The kinematical scaling variable X_(BJ) that represents information about the proton structure cannot be reconstructed in an experiment using a hydrogen target. Thus the X_(BJ) dependence of the cross section for free protons has so far not been accessible. We construct a method that links the measurable distribution in a new variable w₁ that incorporates the hadronic momentum longitudinal and transverse to the beam, to the one in X_(BJ), in a model-independent way. It is shown that even with the statistics of about a thousand events it is possible to recover the X_(BJ) dependence fo the neutrino proton cross-section with appreciable precision. This method is then applied to the data that consists of 2200 neutrino and 1060 antineutrino neutral current events, after correcting for various backgrounds and cuts. We observe a neutral current proton structure that is consistent with the notion of parton universality. The results are compared to two other investigations which employ isoscalar heavy targets, and we find agreement in as far as they are comparable. Furthermore we study the connection between the neutral current structure functions and distributions in the hadronic scaling variable w. It is found that they are related by simple formulae which do not incorporate any dependence on further kinematical variables, in the scaling approximation. We advocate the use of the w dependence of the neutral current cross section as an important piece of information that can provide access to some quantities that are measured only indirectly in charged current and electromagnetic scattering, and to the behaviour of the structure functions at small values of their argument.

Thesis (Honors)--College of William and Mary, 2008. / "This thesis includes work that was published by C.D. Carone and A. Rastogi, Phys. Rev. D." Includes bibliographical references (leaf 85). Also available via the World Wide Web.