Macro dark matter

Dark matter is a vital component of the current best model of our Universe, Λcold dark matter. There are leading candidates for what the dark matter could be (e.g. weakly interacting massive particles, or axions), but no compelling observational or experimental evidence exists to support these particular candidates, nor any beyond-the-Standard-Model physics that might produce such candidates. This suggests that other dark matter candidates, including ones that might arise in the Standard Model, should receive increased attention. Here we consider a general class of dark matter candidates with characteristic masses and interaction cross-sections characterized in units of grams and cm2, respectively – we therefore dub these macroscopic objects as Macros. Such dark matter candidates could potentially be assembled out of Standard Model particles (quarks and leptons) in the early Universe. A combination of Earth-based, astrophysical, and cosmological observations constrain a portion of the Macro parameter space. A large region of parameter space remains, most notably for nuclear-dense objects with masses in the range 55–1017 g and 2 × 1020–4 × 1024 g, although the lower mass window is closed for Macros that destabilize ordinary matter.