Properties of the Magnetic Monopole Plasma

Magnetic monopoles are putative particles having a pure magnetic charge are inevitable in most grand unification theories, though the existing theoretical and observational constraints on the abundance of magnetic monopoles are limited. Here we demonstrate that an ensemble of monopoles forms a plasma whose properties are well determined and whose collective effects cannot be ignored. Coexistence of the tentative monopole plasma and normal plasmas (i.e., ionized gas) in the universe sets the nearly complete equivalence of the monopole plasma and the textbook/classical non-magnetized electron-positron pair plasmas on terms of their basic properties, though spatial and temporal scales are obviously vastly different. We discuss how our findings constrain the abundance of the monopoles in the universe. Certain observational predictions are made.