University of Sussex
Harman, Christopher Peter Dereck.pdf (8.58 MB)
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Very strong and supercool electroweak phase transitions

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posted on 2023-06-09, 08:06 authored by Christopher Peter Dereck Harman
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.


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University of Sussex

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