Dark matter across scales: Ultralight fields, Bose-star signatures, massive compact composites, and giant resonance in dark matter–matter oscillations

Axion- and dilaton-like fields induce stochastic variations in atomic transition frequencies. We develop a statistical framework for clock searches, demonstrating that higher-order moments of frequency fluctuations (variance, skewness, kurtosis, correlators) encode distinctive patterns generated by ultralight dark matter. This approach significantly extends the discovery potential of clock experiments.

Astrophysical implications of self-gravitating bosonic configurations (“Bose stars”) are also analysed. Their interaction with interstellar gas can trigger localised chemical enrichment and seed high-metallicity molecular clouds. These processes offer novel observational pathways for probing bosonic dark matter on macroscopic scales.

A recently identified absorption–ionisation mechanism further broadens the accessible mass range for direct searches in underground laboratories. Dark matter–nucleus scattering, previously assumed incapable of producing detectable signals at low energies, can ionise atoms even for particle masses below 100 keV. This opens a new experimental window long considered unreachable.

Matter and dark matter in galaxies represent two main components linked by the gravitational interaction. Collisions of galaxies may create an offset between the centers of mass of these components. We focus on possible relative oscillations of the matter in a dark matter halo. This two-fluid model is somewhat similar to the "giant dipole resonances'' in nuclei. Such oscillations should manifest themselves as anomalies in the velocities of stars in the galaxy, such as density waves and runaway stars, which have orbit periods in resonance with oscillations.

Models of modified gravity with compact extra dimensions naturally generate strongly singular potentials at short distances. These may stabilise exceptionally dense composite objects formed from quarks or antiquarks, providing another class of dark matter candidates with rich phenomenology and potential astrophysical signatures.

References:
V. V. Flambaum, Phys. Rev. D 112, 015003 (2025)
V. V. Flambaum and I. B. Samsonov, Phys. Rev. D 110, 103016 (2024); Phys. Rev. D 108, 075022 (2023); accepted to MNRAS, arXiv:2511.20952
V. A. Dzuba, V. V. Flambaum, and I. B. Samsonov, Phys. Rev. D 109, 115032 (2024)