Hydrodynamics of the electroweak phase transition

Sopena, Miguel (2013) Hydrodynamics of the electroweak phase transition. Doctoral thesis (PhD), University of Sussex.

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This work investigates the hydrodynamics of the expansion of the bubbles of the broken
symmetry phase during the electroweak phase transition in the early universe, in which
SU(2) electroweak symmetry is broken and fundamental particles acquire mass through the
Higgs mechanism. The electroweak phase transition has received renewed attention as a
viable setting for the production of the matter-antimatter asymmetry of the universe. The
relevant mechanisms are strongly dependent on key parameters like the expansion velocity
of the walls of bubbles of the new phase. In addition, the key dynamical parameters of
the phase transition may generate signatures (like gravitational waves) which may become
detectable in the near future.

This work builds on existing hydrodynamical studies of the growth of bubbles of the
broken symmetry phase and adapts them to novel scenarios, producing predictions of
the wall velocity. The early universe at the time of the electroweak phase transition is
modelled as a perfect relativistic fluid. A fundamental problem is to account for the
interaction between the so-called cosmic ’plasma’ and the bubble wall, which may slow
down wall propagation and produce a steady state with finite velocity. This ’friction’ is
accounted for by a separate term in the hydrodynamical equations. This work adapts
existing microphysical calculations of the friction to two physical models chosen because
of their suitability as regards producing the baryon asymmetry of the universe: 1) An
extension of the Standard Model with dimension-6 operators (for which this is the first
calculation of the wall velocity ever produced) and 2) The Light Stop Scenario (LSS) of
the Minimal Supersymmetric Standard Model (MSSM) (for which this is the first 2-loop
calculation). The predicted values of the wall velocity are coherent and consistent with
previous studies, confirming, in particular, the prediction of a low wall velocity for the

Item Type: Thesis (Doctoral)
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics > QC0120 Descriptive and experimental mechanics > QC0145.2 Fluids. Fluid mechanics. General works
Q Science > QC Physics > QC0251 Heat > QC0310.15 Thermodynamics
Depositing User: Library Cataloguing
Date Deposited: 25 Jul 2013 12:11
Last Modified: 15 Sep 2015 12:53
URI: http://sro.sussex.ac.uk/id/eprint/45752

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