Repulsive ultralight dark matter from Hosotani mechanism
Abstract
We build an ultralight dark matter model with repulsive self-interactions, starting from a 5D action that only includes a U(1) gauge field and several massive and charged free fermions. The dark matter scalar field corresponds to the fifth component of the gauge field, after compactification to 4D. Although the single-fermion case only leads to attractive self-interactions, two fermions can already give rise to repulsive self-interactions, thanks to a Scherk-Schwarz twist around the fifth dimension. We check the observational and theoretical self-consistency of this scenario, from the inflation stage to the current time. We find that large ranges of model parameters are allowed. For scalar masses below 10−12 eV the self-interactions are negligible and the model behaves as fuzzy dark matter. For higher masses the repulsive self-interactions govern the formation of solitons of astrophysical size. Larger sizes require a large initial misalignment or small masses in the fuzzy dark matter regime.
Versions
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BibTeX
@misc{brax2026repulsive,
title = {{Repulsive ultralight dark matter from Hosotani mechanism}},
author = {Philippe Brax and Patrick Valageas},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2607.17727},
eprint = {2607.17727},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.17727},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Repulsive ultralight dark matter from Hosotani mechanism
AU - Philippe Brax
AU - Patrick Valageas
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2607.17727
UR - https://arxiv.org/abs/2607.17727
AB - We build an ultralight dark matter model with repulsive self-interactions, starting from a 5D action that only includes a U(1) gauge field and several massive and charged free fermions. The dark matter scalar field corresponds to the fifth component of the gauge field, after compactification to 4D. Although the single-fermion case only leads to attractive self-interactions, two fermions can already give rise to repulsive self-interactions, thanks to a Scherk-Schwarz twist around the fifth dimension. We check the observational and theoretical self-consistency of this scenario, from the inflation stage to the current time. We find that large ranges of model parameters are allowed. For scalar masses below 10^−12 eV the self-interactions are negligible and the model behaves as fuzzy dark matter. For higher masses the repulsive self-interactions govern the formation of solitons of astrophysical size. Larger sizes require a large initial misalignment or small masses in the fuzzy dark matter regime.
ER -