Microphysical nature of dark matter

Determine the microphysical underpinnings of cold dark matter by identifying the particle or field content, interactions, and action that account for its gravitational effects and cosmological abundance while remaining consistent with precision cosmological observations.

Background

The authors note that, at cosmological scales, dark matter is effectively described by a pressureless fluid, and many candidate microphysical models (e.g., WIMPs, axions/ultralight scalars, primordial black holes) can reproduce the required bulk behavior. Cosmological probes thus provide limited discriminatory power among microphysical candidates.

Non-cosmological searches (direct and indirect detection, astrophysical signatures) have not yet yielded definitive identifications, and large viable parameter spaces remain. This leads to substantial underdetermination of the microphysical theory of dark matter.