Electroweak strings are `worms' of energy which are formed due to the complex interaction of the scalar and gauge fields in a phase transition in the SU(2) x U(1) bosonic sector of the Glashow-Salam-Weinberg model of electroweak physics. Like any defect, these strings correspond to regions of space where the phase transition has been frustrated. If we remove the SU(2) gauge fields, this system reduces to the so-called semilocal strings examined in our previous work.
The additional gauge fields visibly increase the complexity of the system. Now, as well as the line-like strings we also see ball-like magnetic monopoles, with a monopole-antimonopole pair occuring at the ends of the strings. A string with monopoles at the ends is called, for obvious reasons, a dumbbell.
Many such dumbbells form in the phase transition, and while some of them collapse and disappear, others grow by joining to a neighbour. The relative likelihoods of these two modes of evolution depend on the parameters of the model - specifically the ratio of the Higgs and Z-boson masses, and the weak mixing angle. As we vary these parameters, identical initial field configurations will evolve into a persistent or non-persistent string network. Part of the purpose of this work is to establish the line in this 2-parameter space dividing persistence from non-persistence.
Although our results indicate that the actual observed
values of the electroweak theory parameters are well outside the persistent
regime, we have also shown that non-topological defects per se do
form and can persist, and must be taken into account when other phase transitions
These images show the A
and Z fields at three times during
two simulations with the same initial field configurations but with slightly
different field coupling parameters yielding persistent and non-persistent
electroweak string networks.
|Persistent configuration||Non-persistent configuration|
|t = 50|
|t = 200|
|t = 300|
Downloadable mpeg movies of electroweak string evolution
Our largest simulation of electroweak string formation and evolution on a 256x256x256 periodic cubic lattice, showing isosurfaces of the A and Z fields, is available at high (10 Mb) and low (4.5 Mb) temporal resolution.
Our smaller (64x64x64) simulations