Nature of dark matter: particle versus modified gravity

Ascertain whether the astrophysical and cosmological phenomena attributed to dark matter are best explained by a new particle (or particles) or require a modification of Einstein’s General Relativity on galactic and cosmological scales.

Background

Alan Coley and Viraj Sangai outline the standard cosmological model’s reliance on dark matter and dark energy to explain observations. While dark matter is commonly modeled as a particle component, they emphasize that a definitive identification has not been made and that an alternative involving modified gravity remains possible.

This uncertainty has major implications for both particle physics and cosmology, affecting interpretations of galaxy rotation curves, structure formation, and other large-scale phenomena.

References

It is not currently known whether dark matter is to be attributed to a particle or describes some modification of GR.

— The sounds of science a symphony for many instruments and voices part II  (2404.11724 - Hooft et al., 2024) in Section 9: What is the dark energy in cosmology? (Hello darkness, my old friend)

Whether the observed diversity is entirely due to baryonic processes and dynamical modeling, or instead reflects nontrivial properties of DM, therefore remains an open question.

— Diversity of Galaxy Centers from Small-Scale Isocurvature  (2608.21323 - Lopez-Sanchez et al., 21 Aug 2026) in Section 1, Introduction