Nature and properties of dark matter

Determine the fundamental nature and properties of dark matter, specifically establishing the mass of the dark matter particle within the broad range from 10^{-22} eV to 10^{28} eV and resolving which characteristics govern its interactions with Standard Model fields, so that the currently unknown properties are concretely identified and quantified.

Background

The paper motivates atom-interferometric searches for ultralight dark matter and reviews how different spins and couplings would manifest in experiments. At the outset, it emphasizes that while astrophysical evidence for dark matter is strong, its intrinsic properties remain unidentified, including an enormously uncertain mass range. This broad unknown anchors the rationale for developing sensitive laboratory probes, such as ytterbium atom interferometry, to test for oscillatory and static signatures of dark matter across wide parameter space.

The authors outline how various interferometer geometries (spectroscopic, accelerometric, and spin-torque) target specific couplings and signal types. By improving sensitivity to variations of the fine-structure constant, composition-dependent static forces, and axion-induced spin torques, the proposed experiments aim to chip away at the overarching unresolved question: what are the particle properties of dark matter?