Strange quark matter as dark matter: 40 years later, a reappraisal

Understand

Forty years ago Witten suggested that dark matter could be composed of macroscopic clusters of strange quark matter.

• This idea was very popular for several years, but it dropped out of fashion once lattice QCD calculations indicated that the confinement/deconfinement transition, at small baryonic chemical potential, is not first order, which seemed to be a crucial requirement in order to produce large clusters of quarks.
• Here we revisit the conditions under which strangelets can be produced in the Early Universe.
• We discuss the impact of an instability in the hadronic phase separating a low density, positive-strange-charge phase from a high-density phase with a negative strange charge.