The bubble wall velocity in first-order cosmological phase transitions is crucial for phenomenological studies of, for example, the production of stochastic gravitational waves and electroweak baryogenesis. It is commonly expected that a friction force on the bubble wall can only arise from out-of-equilibrium effects. Here we study the bubble wall motion in local thermal equilibrium. We resolve some apparent contradictions in the calculations and their interpretation and show that the recently proposed effective friction in local equilibrium originates from inhomogeneous temperature distributions. Further, we propose a new matching condition from local entropy conservation. With this, we are able to determine the bubble velocities in local equilibrium numerically.  

报告人简介：艾稳元博士，本科及硕士毕业于兰州大学，2019年博士毕业于慕尼黑工业大学。分别于2019-2021年在法语鲁汶大学CP3，2021至今在伦敦国王学院TPPC从事博士后研究。主要研究兴趣为量子场论及非平衡态量子场论，早期宇宙，和粒子物理中的强CP问题。