WallGo documentation

WallGo is an open source code for the computation of the bubble wall velocity and bubble wall width in first-order cosmological phase transitions. If you use WallGo, please cite the WallGo paper JHEP 04 (2025) 101. [1]

As the universe cooled after the Hot Big Bang, it may have gone through any number of cosmological first-order phase transitions. Such transitions proceed via the nucleation and growth of bubbles, as shown in the image below. [2] The collisions of these bubbles may lead to an observable gravitational wave signal today, depending on the speed of the bubble walls as they collide.

How fast does the bubble wall go? WallGo is a Python package for answering this question. Our methods largely follow previous work by Laurent and Cline. [3]

References

[1]

Andreas Ekstedt, Oliver Gould, Joonas Hirvonen, Benoit Laurent, Lauri Niemi, Philipp Schicho, and Jorinde van de Vis. How fast does the WallGo? A package for computing wall velocities in first-order phase transitions. JHEP, 04:101, 2025. arXiv:2411.04970, doi:10.1007/JHEP04(2025)101.

[2]

David Weir. Simulation of a cosmological thermal phase transition, early times. https://commons.wikimedia.org/wiki/File:Simulation_of_a_cosmological_thermal_phase_transition,_early_times.jpg, 2016.

[3]

Benoit Laurent and James M. Cline. First principles determination of bubble wall velocity. Phys. Rev. D, 106(2):023501, 2022. arXiv:2204.13120, doi:10.1103/PhysRevD.106.023501.