Takumi Hayashi (Tokyo/RESCEU) gave a talk on Lorenzian path-integral approach to false vacuum decay [1]. Conventionally, false vacuum decay has been discussed within the Euclidean formalism developed by Coleman, but it may suffer from several subtle issues when applying to cosmological problems. Takumi proposed a new formulation for false vacuum decay and computed the bubble nucleation rate by directly evaluating a Lorenzian path integral based on the Picard-Lefschetz theory. Takumi discussed nucleation of bubbles with various sizes, not limited to the critical one only to which the Euclidean formalism can be applied, and showed that nucleation of small bubbles is more probable than the critical one. More than 20 physicists have joined the seminar and enjoyed fruitful discussions.

Reported by Hidetoshi Taya


  1. T. Hayashi, K. Kamada, N. Oshita, and J. Yokoyama, Vacuum decay in the Lorentzian path integral, hep-th (2021), arXiv: 2112.09284