Magnetic seed field generation from electroweak bubble collisions with bubble walls of finite thickness

Abstract

Building on earlier work, we develop an equation-of-motion method for calculating magnetic seed fields generated from currents arising from charged ${W}^{\ifmmode\pm\else\textpm\fi{}}$ fields in bubble collisions during a first-order primordial electroweak phase transition allowed in some proposed extensions of the standard model. The novel feature of our work is that it takes into account, for the first time, the dynamics of the bubble walls in such collisions. We conclude that for bubbles with sufficiently thin surfaces the magnetic seed fields may be comparable to, or larger than, those found in earlier work. Thus, our results strengthen the conclusions of previous studies that cosmic magnetic fields observed today may originate from seeds created during the electroweak phase transition, and consequently that these fields may offer a clue relevant to extensions of the standard model.