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.

There are simple models based on Yukawa interaction between dark matter particles that are fully consistent with all astrophysical constraints. These models also, remarkably, explain the diverse rotation curves seen in spiral galaxies in a manner that is compatible with a wide range of stellar feedback models. CDM models currently have difficulty doing so.


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 and effects of modified gravity? This review is devoted to discussing these questions.

Review Outline (in prep.)

  1. Introduction and Theory

    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. Physical Effects in Galaxies and Clusters

    1. SIDM density profile and its shape.  [Dwarf galaxies to clusters of galaxies]

    2. Lack of dynamical friction in cored halos. [Clusters, UDGs, LSBs, dwarf galaxies]

    3. Enhanced Gravitational Tidal Stripping of Cored Subhalos [Galactic and cluster satellites like UDGs]

    4. Drag Force and Mass Loss due to Self-Interactions

    5. Large scale structure of SIDM models

    6. Gravothermal collapse of SIDM haloes

    7. Mass loss due to self-interactions. [Clusters and Galactic satellites]

    8.  Are these physical effects unique
  3. Observations of SIDM

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

    2. X-ray and Weak Lensing Observations of Clusters, Groups and Large Ellipticals

    3. Major and minor mergers in groups and clusters.

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

    5. Rotation and dispersion measures of high redshift galaxies.

    6. Dwarf Galaxies in the Local Group and beyond

    7. Rotation curves of spiral galaxies

    8. Ultra-diffuse galaxies in clusters

  4.  Extensions of the simple SIDM model

    1. SIDM with dissipation

    2. SIDM as a DM subcomponent

    3. SIDM with late kinetic decoupling

  5.  Complementary constraints on SIDM models

    1. Light mediators and Sommerfeld enhancement

    2. Strongly-interacting massive particles