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arXiv · 2608.03678

Hierarchical Axiverse

Hai-Jun Li
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Abstract

String compactifications generically produce ${\cal O}(100)$ light axion-like particles, yet low-energy mixing has not previously been exploited as a structuring constraint on their spectrum. We show that the requirement of well-defined QCD-induced mass mixing forces the axion masses into a hierarchically spaced ordering, while stochastic mixing organizes the decay constants into a hierarchically split distribution -- two populations separated by an essentially empty window. Both patterns are insensitive to ultraviolet input and satisfy the relevant Swampland constraints within standard large-volume compactifications. We term this emergent pattern the hierarchical axiverse.

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Hai-Jun Li. 2026-08-04. Hierarchical Axiverse. https://arxiv.org/abs/2608.03678

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