Primordial magnetic fields at preheating

Departamento de Fisica Teorica and Instituto de Fisica Teorica UAM-CSICUniversidad Autonoma de Madrid, Cantoblanco, 28049 Madrid, Spainantonio.gonzalez-arroyo@uam.esUsing lattice techniques we investigate the generation of long range cosmological magnetic fieldsduring a cold electroweak transition. We will show how magnetic fields arise, during bubblecollisions, in the form of magnetic strings. We conjecture that these magnetic strings originatefrom the alignment of magnetic dipoles associated with EW sphaleron-like configurations. Wealso discuss the early thermalisation of photons and the turbulent behaviour of the scalar fieldsafter tachyonic preheating.The XXV International Symposium on Lattice Field TheoryJuly 30 - August 4 2007Regensburg, Germany