Determine the nature and properties of dark matter

Determine the fundamental nature and properties of dark matter that account for its cosmological abundance and astrophysical effects, including identifying whether dark matter consists of primordial black holes or new particles beyond the Standard Model, so as to resolve the Standard Model’s lack of an explanation for the dominant matter component of the Universe.

Background

The paper motivates its study by emphasizing that the Standard Model does not explain the dominant matter component of the Universe. Observational evidence across cosmological scales requires a dark matter component, yet its particle or non-particle nature and properties remain unknown.

This uncertainty frames the investigation of primordial black holes and heavy neutral leptons as potential probes. By analyzing signals from hypothetical nearby PBH explosions, the authors explore how multimessenger observations (neutrinos at IceCube and gamma rays at HAWC) could constrain beyond-Standard-Model scenarios, but the overarching open problem of dark matter’s nature and properties persists.

References

Numerous observations at different cosmological scales indicate that most matter in the Universe is made up of dark matter (DM), whose nature and properties are still unknown.

— Primordial black hole probes of heavy neutral leptons  (2405.00124 - Romeri et al., 2024) in Introduction

(ii) unknown unknowns: this part covers sectors where we still do not know how they vary and impact black hole evolution.

— Bridging Between Statistical Mechanics and Black Hole Evolution: Theoretical Formalism  (2609.16534 - Mukherjee, 15 Sep 2026) in Section 2, Motivation

Within the $ framework, CDM has not been associated with any known elementary particle, and its nature remains an open question.

— Distinguishing cold and self-interacting dark matter through topological analysis  (2608.25632 - Szpilfidel et al., 26 Aug 2026) in Section 1, Introduction

Current constraints exclude PBHs from making up all of the DM, apart from in the ‘asteroid mass window’ ($10{ 17} g \lesssim M \lesssim10{22}g$)” (op.cit., p. 11). This still permissible range isn’t motivated by independent principles or other considerations. Instead, it’s a brute fact whittling down due to data---last retreats in an ever-shrinking parameter space: that the asteroid-mass region remains open ``largely reflects the difficulty of detecting such light compact objects” \parencite[p. 23]{GreenKavanagh2021PBHDarkMatter}.

— Dark Matters of Principle: Principles in the Dark Matter Paradigm  (2608.25954 - Duerr et al., 26 Aug 2026) in Section 4, subsection “Primordial black holes,” introductory discussion of ad hocness, third item