Ultra-Strongly Self-Interacting Dark Matter: From Phenomenology to Astrophysical Observables

2025/10/20 by M. Grant Roberts, Wolfgang Altmannshofer, Roberts, M. Grant +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Physics - Phenomenology (hep-ph)

paper · pdf · doi:10.48550/arxiv.2510.18142

openalex publication_date 2025/10/20 · openalex created_date 2025/10/24 · openalex updated_date 2026/07/28

Abstract

We develop a minimal, testable framework for two-component self-interacting dark matter (SIDM) in which a dominant, moderately self-interacting species coexists with an ultra-strongly self-interacting subcomponent (uSIDM). A light vector mediator induces velocity-dependent self-scattering, while early-universe dynamics - standard 2 → 2 annihilation supplemented by interconversion χ₁χ₁ → χ₂χ₂ - determine the relic abundance analytically. From observations of dwarf and low surface brightness galaxy rotation curves, as well as strong cluster lensing, we place constraints on the microphysics parameters. From these constrained regions, we map the microphysics to effective ETHOS parameters and evolve the linear power spectrum in CLASS. We then confront the model with direct-detection constraints and place an upper bound on our parameter space. We identify a region where: (1) the SIDM dominant component attains σ_\rmeff/m = 20 - 40~cm²g^-1 at dwarf velocities while satisfying cluster upper bounds σ_\rmeff/m < 0.13~\rmcm²\rmg^-1; (2) a subpercent uSIDM fraction drives accelerated gravothermal collapse in early halos, providing seeds relevant to high-redshift quasar formation and ``little red dots''; and (3) the small-scale cutoff in the matter power spectrum remains consistent with Lyman-α and satellite counts, but exhibits non-standard features, potentially discernible with future observations. The allowed space can be organized by the mediator-to-DM mass ratio and the late-time uSIDM fraction, with a narrow window singled out by the combined cosmological and astrophysical requirements.

Citations

• A Constraint on Dark Matter Self-Interaction from Combined Strong Lensing and Stellar Kinematics in MACS J0138-2155
• Little Red Dots from Ultra-Strongly Self-Interacting Dark Matter
• Diversifying halo structures in two-component self-interacting dark matter models via mass segregation
• Gravothermal collapse and the diversity of galactic rotation curves
• Dust in Little Red Dots
• A Census of Photometrically Selected Little Red Dots at 4 < z < 9 in JWST Blank Fields
• On the Late-Time Evolution of Velocity-Dependent Self-Interacting Dark Matter Halos
• Milky Way satellite velocities reveal the Dark Matter power spectrum at small scales
• Hydrogen Epoch of Reionization Array (HERA)
• Constraints on Light Hidden Sector Gauge Bosons from Supernova Cooling
• Cosmic abundances of stable particles: Improved analysis

Related

• Self-interacting Dark Matter in Non-Standard Cosmology
• Self-interacting Dark Matter Benchmarks
• Self-Interacting Dark Matter with Mass Segregation: A Unified Explanation of Dwarf Cores and Small-Scale Lenses
• Astrophysical Tests of Dark Matter Self-Interactions
• Stringent Constraints on Self-Interacting Dark Matter Using Milky-Way Satellite Galaxies Kinematics