SU(𝒩) baryon formation in the early Universe and dark matter
Abstract
We study the formation of 𝒩-quark baryons during the confinement crossover of an SU(𝒩) gauge theory containing quarks in the fundamental representation, with masses around or below the confinement scale. We assume stepwise baryon formation through the successive fusion of pairs of quark-clusters, with color interaction rates obeying quadratic Casimir scaling. We include the complete set of reactions between SU(𝒩) antisymmetric clusters dressed with their specific spin-flavor multiplicities. We show that at large 𝒩, baryon formation is hindered by a Casimir bottleneck, such that fusion of few-quark clusters in the initial steps of the baryon assembly chain is strongly outweighed by cluster destruction processes. We find that for 𝒩=12 (18) the baryon-to-meson yield ratio is suppressed down to 10−12 (10−23) of its value at 𝒩=3. We embed the mechanism in a vectorlike three-flavor model whose lightest baryon can be electrically neutral, while axial-anomaly-induced couplings and dimension-six operators induce decays of the unstable mesons and charged baryons safely before big-bang nucleosynthesis. The relic density of cosmologically stable neutral 𝒩-baryons is thus set during confinement at values so small that, for sufficiently large 𝒩, the baryon masses required to saturate the dark matter energy density exceed by several orders of magnitude the unitarity bound on annihilation cross sections.
Related
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- Right-handed neutrino dark matter consistent with the generation of baryon number asymmetry
BibTeX
@misc{luzio2026su𝒩,
title = {{$SU(\mathcalN)$ baryon formation in the early Universe and dark matter}},
author = {Luca Di Luzio and Samuele Di Valeriano and Enrico Nardi},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.02464},
eprint = {2610.02464},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.02464},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - SU(𝒩) baryon formation in the early Universe and dark matter
AU - Luca Di Luzio
AU - Samuele Di Valeriano
AU - Enrico Nardi
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.02464
UR - https://arxiv.org/abs/2610.02464
AB - We study the formation of 𝒩-quark baryons during the confinement crossover of an SU(𝒩) gauge theory containing quarks in the fundamental representation, with masses around or below the confinement scale. We assume stepwise baryon formation through the successive fusion of pairs of quark-clusters, with color interaction rates obeying quadratic Casimir scaling. We include the complete set of reactions between SU(𝒩) antisymmetric clusters dressed with their specific spin-flavor multiplicities. We show that at large 𝒩, baryon formation is hindered by a Casimir bottleneck, such that fusion of few-quark clusters in the initial steps of the baryon assembly chain is strongly outweighed by cluster destruction processes. We find that for 𝒩=12 (18) the baryon-to-meson yield ratio is suppressed down to 10^−12 (10^−23) of its value at 𝒩=3. We embed the mechanism in a vectorlike three-flavor model whose lightest baryon can be electrically neutral, while axial-anomaly-induced couplings and dimension-six operators induce decays of the unstable mesons and charged baryons safely before big-bang nucleosynthesis. The relic density of cosmologically stable neutral 𝒩-baryons is thus set during confinement at values so small that, for sufficiently large 𝒩, the baryon masses required to saturate the dark matter energy density exceed by several orders of magnitude the unitarity bound on annihilation cross sections.
ER -