Most grand unified theories predict their existence at a density such that a small loop of superconducting wire should be able to detect one per year, but none have been detected yet, even in searches of lunar rocks.
They are admitted as topological defects, a special case of dyons, and are generally supermassive. One-dimensional analogues of cosmic strings, they were posited by Dirac to explain conservation of angular momentum and charge. Most grand unified theories predict their existence at a density such that a small loop of superconducting wire should be able to detect one per year, but none have been detected yet, even in searches of lunar rocks. They are classically forbidden, since the field they ostensibly generate must be divergence-free by Gauss' law for it. FTP, name these hypothetical charges; theoretical sources for the magnetic field.
They are admitted as topological defects, a special case of dyons, and are generally supermassive.
magnetic monopoles (or magnetic charges)