Macro Dark Matter
  Dark matter is a vital component of the current best model of our universe,
$\Lambda$CDM. 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
cm$^2$, 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 $55 - 10^{17}$ g and
$2\times10^{20} - 4\times10^{24}$ g, although the lower mass window is closed
for Macros that destabilize ordinary matter.
