How fast does the WallGo? A package for computing wall velocities in first-order phase transitions

Abstract WallGo is an open-source software designed to compute the bubble wall velocity in first-order cosmological phase transitions. Additionally, it evaluates the energy budget available for generating gravitational waves. The main part of WallGo, built in Python, determines the wall velocity by...

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Main Authors: Andreas Ekstedt, Oliver Gould, Joonas Hirvonen, Benoit Laurent, Lauri Niemi, Philipp Schicho, Jorinde van de Vis
Format: Article
Language:English
Published: SpringerOpen 2025-04-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP04(2025)101
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author Andreas Ekstedt
Oliver Gould
Joonas Hirvonen
Benoit Laurent
Lauri Niemi
Philipp Schicho
Jorinde van de Vis
author_facet Andreas Ekstedt
Oliver Gould
Joonas Hirvonen
Benoit Laurent
Lauri Niemi
Philipp Schicho
Jorinde van de Vis
author_sort Andreas Ekstedt
collection DOAJ
description Abstract WallGo is an open-source software designed to compute the bubble wall velocity in first-order cosmological phase transitions. Additionally, it evaluates the energy budget available for generating gravitational waves. The main part of WallGo, built in Python, determines the wall velocity by solving the scalar-field(s) equation of motion, the Boltzmann equations and energy-momentum conservation for the fluid velocity and temperature. WallGo also includes two auxiliary modules: WallGoMatrix, which computes matrix elements for out-of-equilibrium particles, and WallGoCollision, which performs higher-dimensional integrals for Boltzmann collision terms. Users can implement custom models by defining an effective potential and specifying a list of out-of-equilibrium particles and their interactions. As the first public software to compute the wall velocity including out-of-equilibrium contributions, WallGo improves the precision of the computation compared to common assumptions in earlier computations. It utilises a spectral method for the deviation from equilibrium and collision terms that provides exponential convergence in basis polynomials, and supports multiple out-of-equilibrium particles, allowing for Boltzmann mixing terms. WallGo is tailored for non-runaway wall scenarios where leading-order coupling effects dominate friction. While this work introduces the software and the underlying theory, a more detailed documentation can be found in https://wallgo.readthedocs.io .
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spelling doaj-art-a9192252d78f49c898e2fd9a7716db2d2025-08-20T03:09:34ZengSpringerOpenJournal of High Energy Physics1029-84792025-04-012025416510.1007/JHEP04(2025)101How fast does the WallGo? A package for computing wall velocities in first-order phase transitionsAndreas Ekstedt0Oliver Gould1Joonas Hirvonen2Benoit Laurent3Lauri Niemi4Philipp Schicho5Jorinde van de Vis6Department of Physics and Astronomy, Uppsala UniversitySchool of Physics and Astronomy, University of NottinghamSchool of Physics and Astronomy, University of NottinghamDepartment of Physics, McGill UniversityDepartment of Physics and Helsinki Institute of Physics, University of HelsinkiDépartement de Physique Théorique, Université de GenèveTheoretical Physics Department, CERNAbstract WallGo is an open-source software designed to compute the bubble wall velocity in first-order cosmological phase transitions. Additionally, it evaluates the energy budget available for generating gravitational waves. The main part of WallGo, built in Python, determines the wall velocity by solving the scalar-field(s) equation of motion, the Boltzmann equations and energy-momentum conservation for the fluid velocity and temperature. WallGo also includes two auxiliary modules: WallGoMatrix, which computes matrix elements for out-of-equilibrium particles, and WallGoCollision, which performs higher-dimensional integrals for Boltzmann collision terms. Users can implement custom models by defining an effective potential and specifying a list of out-of-equilibrium particles and their interactions. As the first public software to compute the wall velocity including out-of-equilibrium contributions, WallGo improves the precision of the computation compared to common assumptions in earlier computations. It utilises a spectral method for the deviation from equilibrium and collision terms that provides exponential convergence in basis polynomials, and supports multiple out-of-equilibrium particles, allowing for Boltzmann mixing terms. WallGo is tailored for non-runaway wall scenarios where leading-order coupling effects dominate friction. While this work introduces the software and the underlying theory, a more detailed documentation can be found in https://wallgo.readthedocs.io .https://doi.org/10.1007/JHEP04(2025)101Phase Transitions in the Early UniverseEarly Universe Particle Physics
spellingShingle Andreas Ekstedt
Oliver Gould
Joonas Hirvonen
Benoit Laurent
Lauri Niemi
Philipp Schicho
Jorinde van de Vis
How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
Journal of High Energy Physics
Phase Transitions in the Early Universe
Early Universe Particle Physics
title How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
title_full How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
title_fullStr How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
title_full_unstemmed How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
title_short How fast does the WallGo? A package for computing wall velocities in first-order phase transitions
title_sort how fast does the wallgo a package for computing wall velocities in first order phase transitions
topic Phase Transitions in the Early Universe
Early Universe Particle Physics
url https://doi.org/10.1007/JHEP04(2025)101
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