Secluded Majorana SIDM: Velocity-Dependent Self-Interactions from a Light Scalar Mediator
Authors/Creators
Description
A Majorana fermion χ coupled to a light scalar mediator φ through a Yukawa interaction provides a minimal model for self-interacting dark matter (SIDM). We compute velocity-dependent transfer cross sections using the Variable Phase Method (VPM) — a full partial-wave analysis that captures resonance structure missed by the Born approximation (which overestimates by 88–135×). The model yields σ/m = 0.5–0.8 cm²/g on dwarf scales (v ~ 30 km/s) and σ/m = 0.07–0.10 cm²/g on cluster scales (v ~ 1000 km/s), fitting 13 astrophysical systems with χ²/ν = 0.38. Relic density is computed via exact Boltzmann integration, giving Ωh² = 0.120. The secluded sector predicts null direct detection (σ_SI = 0) and negligible ΔN_eff. Code, data, and figures included.
Notes
Key results:
- Island of viability: m_χ ∈ [10, 100] GeV, m_φ ∈ [7.6, 14.8] MeV
- Velocity-dependent cross sections spanning dwarfs to clusters
- Born approximation fails catastrophically — VPM required
- Exact relic density from Boltzmann equation (not freeze-out approximation)
- Zero free parameters after fixing {m_χ, m_φ, α_s} to astrophysical data
Contents: Python source code (VPM solver, Boltzmann integrator, MCMC fitter), all figures, numerical output tables, and the compiled manuscript (main.pdf).
Related: This is Paper 1 in a series. Paper 2 (DOI: 10.5281/zenodo.19274637) extends the model to dark energy via a dark QCD axion.
Files
main.pdf
Files
(35.3 MB)
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Additional details
Software
- Repository URL
- https://github.com/0mp3s/Secluded-Majorana-SIDM