Z-vortex percolation in the electroweak crossover region

We study the statistical properties of Z-vortices and Nambu monopoles in th e 3D SU(2) Higgs model fur a Higgs mass M-H approximate to 100 GeV near and above die crossover temperature, where these defects are thermally excited . Although there is no phase transition at that strong selfcoupling, we obs erve that the Z-vortices exhibit the percolation transition that has been f ound recently to accompany the first order thermal transition that exists a t smaller Higgs mass. Above the crossover temperature percolating networks of Z-vortex lines are ubiquitous, whereas vortices form a dilute gas of clo sed vortex loops and (Nambu) monopolium states on the low-temperature side of the crossover. The percolation temperature turns out to be roughly indep endent of the lattice spacing. We find that the Higgs modulus is smaller (t he gauge action is larger) inside the vortices, compared to the bulk averag e. This correlation becomes very strong on the low-temperature side. The pe rcolation transition is a prerequisite of some string mediated baryon numbe r generation scenarios. (C) 1998 Published by Elsevier Science B.V. All rig hts reserved.