Towards an all-orders calculation of the electroweak bubble wall velocity

We analyze Higgs condensate bubble expansion during a first-order electroweak phase transition in the early Universe. The interaction of particles with the bubble wall can be accompanied by the emission of multiple soft gauge bosons. When computed at fixed order in perturbation theory, this process exhibits large logarithmic enhancements which must be resummed to all orders when the wall velocity is large. We perform this resummation both analytically and numerically at leading logarithmic accuracy. The numerical simulation is achieved by means of a particle shower in the broken phase of the electroweak theory. The two approaches agree to the 10% level. For fast-moving walls, we find the scaling of the thermal pressure exerted against the wall to be P similar to gamma T-2(4), independent of the particle masses, implying a significantly slower terminal velocity than previously suggested.

Automated summary

In this study, we analyzed the expansion of Higgs condensate bubbles during a first-order electroweak phase transition in the early Universe. The interaction of particles with the bubble wall may involve the emission of multiple soft gauge bosons. Resummation to all orders is necessary when the wall velocity is large, and we performed this resummation analytically and numerically at leading logarithmic accuracy. Both approaches agreed to a 10% level, and for fast-moving walls, we found a scaling of the thermal pressure exerted against the wall.