Bubble wall velocity from Kadanoff-Baym equations: fluid dynamics and microscopic interactions

Fuente: arXiv
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Autores principales: Ramsey-Musolf, Michael J., Zhu, Jiang
Formato: Preprint
Publicado: 2025
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author Ramsey-Musolf, Michael J.
Zhu, Jiang
author_facet Ramsey-Musolf, Michael J.
Zhu, Jiang
contents We establish a first principles, systematic framework for determining the bubble wall velocity during a first order cosmological phase transition. This framework, based on non-local Kadanoff-Baym equations, incorporates both macroscopic fluid dynamics and microscopic interactions between the bubble wall and particles in the plasma. Previous studies have generally focused on one of these two sources of friction pressure that govern the wall velocity. As a precursor, we utilize background field quantum field theory to obtain the relevant local Boltzmann equations, from which we derive the forces associated with variation of particle masses across the bubble wall and the microscopic wall-particle interactions. We subsequently show how these equations emerge from the Kadanoff-Baym framework under various approximations. We apply this framework in the ballistic regime to compute the new friction force arising from the $2\rightarrow 2$ scattering processes in scalar field theory. We obtain a linear relationship between this force and the Lorentz factor $γ_w$ that would preclude runaway bubbles with such effects.
format Preprint
id arxiv_https___arxiv_org_abs_2504_13724
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Bubble wall velocity from Kadanoff-Baym equations: fluid dynamics and microscopic interactions
Ramsey-Musolf, Michael J.
Zhu, Jiang
High Energy Physics - Phenomenology
High Energy Physics - Theory
We establish a first principles, systematic framework for determining the bubble wall velocity during a first order cosmological phase transition. This framework, based on non-local Kadanoff-Baym equations, incorporates both macroscopic fluid dynamics and microscopic interactions between the bubble wall and particles in the plasma. Previous studies have generally focused on one of these two sources of friction pressure that govern the wall velocity. As a precursor, we utilize background field quantum field theory to obtain the relevant local Boltzmann equations, from which we derive the forces associated with variation of particle masses across the bubble wall and the microscopic wall-particle interactions. We subsequently show how these equations emerge from the Kadanoff-Baym framework under various approximations. We apply this framework in the ballistic regime to compute the new friction force arising from the $2\rightarrow 2$ scattering processes in scalar field theory. We obtain a linear relationship between this force and the Lorentz factor $γ_w$ that would preclude runaway bubbles with such effects.
title Bubble wall velocity from Kadanoff-Baym equations: fluid dynamics and microscopic interactions
topic High Energy Physics - Phenomenology
High Energy Physics - Theory
url https://arxiv.org/abs/2504.13724