Upper Bound on the Cosmic Baryon Chemical Potential from Lepton-Flavor Asymmetry

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Main Authors: Di Clemente, Francesco, Drago, Alessandro, Formaggio, Lorenzo, Ratti, Claudia, Vovchenko, Volodymyr, Yadav, Geetika
Format: Preprint
Published: 2025
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author Di Clemente, Francesco
Drago, Alessandro
Formaggio, Lorenzo
Ratti, Claudia
Vovchenko, Volodymyr
Yadav, Geetika
author_facet Di Clemente, Francesco
Drago, Alessandro
Formaggio, Lorenzo
Ratti, Claudia
Vovchenko, Volodymyr
Yadav, Geetika
contents We study the early Universe trajectory around the QCD transition in lepton-flavor-asymmetric cases with small total lepton asymmetry ($|\ell|\lesssim 10^{-2}$), while allowing large individual lepton asymmetries. For each temperature, we find an upper bound on the baryon chemical potential $μ_{\mathrm B}(T)$: $τ$--$μ$ asymmetric cases exhibit a local maximum, whereas $μ$--$e$ cases approach a limiting curve. Thus, even extreme lepton-flavor asymmetry alone cannot reach a first-order region, unless the critical point is moved to a substantially lower $μ_\mathrm{B}/T$ because of the nonzero $μ_\mathrm{Q}$. Therefore, we constrain the QCD-era relic to the standard scenario of a chiral crossover transition.
format Preprint
id arxiv_https___arxiv_org_abs_2511_11995
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Upper Bound on the Cosmic Baryon Chemical Potential from Lepton-Flavor Asymmetry
Di Clemente, Francesco
Drago, Alessandro
Formaggio, Lorenzo
Ratti, Claudia
Vovchenko, Volodymyr
Yadav, Geetika
High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
We study the early Universe trajectory around the QCD transition in lepton-flavor-asymmetric cases with small total lepton asymmetry ($|\ell|\lesssim 10^{-2}$), while allowing large individual lepton asymmetries. For each temperature, we find an upper bound on the baryon chemical potential $μ_{\mathrm B}(T)$: $τ$--$μ$ asymmetric cases exhibit a local maximum, whereas $μ$--$e$ cases approach a limiting curve. Thus, even extreme lepton-flavor asymmetry alone cannot reach a first-order region, unless the critical point is moved to a substantially lower $μ_\mathrm{B}/T$ because of the nonzero $μ_\mathrm{Q}$. Therefore, we constrain the QCD-era relic to the standard scenario of a chiral crossover transition.
title Upper Bound on the Cosmic Baryon Chemical Potential from Lepton-Flavor Asymmetry
topic High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
url https://arxiv.org/abs/2511.11995