Dynamics of Topological Defects in Electroweak Theory

Our understanding of the mechanism by which topological defects are formed in symmetry breaking phase transitions has recently changed. We examine the non-equilibrium dynamics of defect formation for weakly-coupled global O(N) theories possessing vortices (strings) and monopoles. It is seen that, as domains form and grow, defects are swept along on their boundaries at a density of about one defect per coherence area (strings) or per coherence volume (monopoles).

It is argued that confining effects in 3-dimensional non-Abelian gauge theories (high-temperature limit of 4-dimensional ones) imply the existence of the condensates of the gauge and Higgs fields in 3-d vacuum. This non-perturbative effect can decrease the energy of the phase with unbroken symmetry and may result in the creation of a barrier separating the broken and unbroken phases. Thus the high-temperature phase transitions in gauge theories can be stronger first order tha...

We demonstrate the existence of global monopole and vortex configurations whose core exhibits a phase structure. We determine the critical values of parameters for which the transition from the symmetric to the non-symmetric phase occurs and discuss the novel dynamics implied by the non-symmetric cores for defect interactions. We model phase transitions in the core of global embedded topological defects by identifying the relevant parameters with the vacuum expectation value ...

Classical defects (monopoles, vortices, etc.) are a characteristic consequence of many phase transitions of quantum fields. Most likely these include transitions in the early universe and such defects would be expected to be present in the universe today. We continue our analysis of the onset of classical behaviour after a second-order phase transition in quantum field theory and show how defects appear after such transitions

This talk summarises recent results on lattice Monte Carlo studies of finite T electroweak phase transition. Particular attention is given to the 3d effective theory approach, replacing the full 4d theory by a three dimensional effective theory of the modes constant in imaginary time.

We study first-order electroweak phase transitions nonperturbatively, assuming any particles beyond the Standard Model are sufficiently heavy to be integrated out at the phase transition. Utilising high temperature dimensional reduction, we perform lattice Monte-Carlo simulations to calculate the main quantities characterising the transition: the critical temperature, the latent heat, the surface tension and the bubble nucleation rate, updating and extending previous lattice ...

We examine the formation of vortices during the nonequilibrium relaxation of a high-temperature initial state of an Abelian-Higgs system. We equilibrate the scalar and gauge fields using gauge-invariant Langevin equations and relax the system by instantaneously removing thermal fluctuations. For couplings near critical we observe the formation of large clusters of like-sign magnetic vortices. Their appearance has implications for the dynamics of the phase transition, for the ...

We present results obtained from a numerical investigation of the electroweak phase transition in the SU(2)-Higgs model. The simulations are performed at two values of the Higgs boson mass, $M_H\approx 20$ GeV and $M_H\approx 50$ GeV. While the phase transition is of strongly first order at the smaller value of the Higgs mass it weakens rapidly when the Higgs mass is increased. This is in qualitative agreement with perturbation theory as the comparison of various physical qua...

Using a simplified lattice version of the electroweak sector of the standard model, with dynamical fermions excluded, we determine at fixed Weinberg angle the transition line between the confined phase and the Higgs phase, the latter defined as the region where the global center subgroup of the gauge group is spontaneously broken, and "separation of charge" confinement disappears. We then search, via lattice Monte Carlo simulations, for possible neutral vector bosons in the H...

Recent developments on the four dimensional (4d) lattice studies of the finite temperature electroweak phase transition (EWPT) are summarized. The phase diagram is given in the continuum limit. The finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses m_H<66.5 +/- 1.4 GeV. Above this endpoint only a rapid cross-over can be seen. The full 4d result agrees completely with that of the dimensional reduction approximation. The Higgs-boson endpoin...