Self-Interacting Dark Matter


Strongly self-interacting dark matter (SIDM) is an idea that inherits all the large-scale successes of the cold dark matter paradigm but makes different predictions for stellar and dark matter distribution in galaxies and galaxy clusters at radii smaller than roughly 10% of the virial radius.

SIDM was motivated by the cusp-core and missing satellites problems on galaxy scales. There are simple models based on Yukawa interaction between dark matter particles that address these issues and are fully consistent with all astrophysical constraints. These models may also explain the diverse rotation curves seen in spiral galaxies more efficiently than CDM models.


Which observations are suited for testing self-interaction of dark matter particles? How much better are the constraints on SIDM models expected to get? Is it possible to rule out or confirm that dark matter is strongly self-interacting based on astrophysical observations in the next 5-10 years? And finally, what are the degeneracies between SIDM, baryonic effects and modified gravity? This review is devoted to these questions.

Link to review

Review Outline

  1. Introduction

    1. The basic concepts and a brief history

    2. The effective physical phenomena arising from microscopic interactions: elastic scattering

    3. Velocity and angle dependent scattering

  2. Theoretical considerations

    1. What we mean by cross-section

    2. Macrophysical phenemona from microphysical interactions


    Physical effects in galaxies and clusters

    1. Core formation with SIDM

    2. Gravothermal collapse of SIDM halos

    3. Lack of dynamical friction in cored halos

    4. Enhanced gravitational tidal stripping of cored subhalos

    5. Halo shapes

    6. Drag force and mass loss due to self-interactions

    7. Large scale structure of SIDM models

    8. Are these physical effects unique?
  4. Observations of SIDM

    1. Strong gravitational lensing in clusters, groups and large ellipticals.

    2. Stellar streams in the Milky Way

    3. X-ray and weak lensing observations of clusters, groups and large ellipticals

    4. Major and minor mergers in groups and clusters.

    5. Incidence of multiple BCGs, their stellar kinematics and their spatial separations.

    6. Dwarf galaxies in the Local Group and beyond

    7. Rotation curves of spiral galaxies

    8. Ultra-diffuse galaxies in clusters

    9. Warping of stellar disks

    10. Large-scale structure constraints

    11. Summary of constraints on the cross section

  5.  Beyond the simple SIDM framework

    1. SIDM with dissipation

    2. Subcomponent SIDM

    3. Phenomenology of light mediators

    4. Connections for the Standard Model

  6.  Future prospects

    1. Observational probes

    2. Simulations and modelling

    3. Promising tests of simple SIDM models