EMBEDDED TOPOLOGICAL DEFECTS IN HOT ELECTROWEAK THEORY - A LATTICE STUDY

We study the properties of Nambu monopoles and Z-vortices in the 3D la ttice SU(2) Higgs theory which represents the Standard Model at high t emperature. We show that the densities of the Nambu monopoles and the Z-vortices are O(1) in the symmetric phase and generically small in th e Higgs phase. Near to the critical Higgs mass and in the vicinity of the phase transition the densities are no more negligible in the broke n phase. The percolation probability of the Z-vortex lines is found as a new disorder parameter for this phase transition. We conclude that the transition to the symmetric phase is accompanied by Z-vortex conde nsation. Simulations comparing elementary and extended vortices and mo nopoles at different beta(G) values, aiming to show that the density o f vortices and monopoles of fixed physical size might have a well-defi ned continuum limit, gives encouraging but so far inconclusive results . (C) 1998 Published by Elsevier Science B.V. All rights reserved.