  Quantum electrodynamics predicts that in a strong electric field,
electron-positron pairs are produced by the Schwinger process, which can be
interpreted as quantum tunnelling through the Coulomb potential barrier. If
magnetic monopoles exist, monopole-antimonopole pairs would be similarly
produced in strong magnetic fields by the electromagnetic dual of this process.
The production rate can be computed using semiclassical techniques without
relying on perturbation theory, and therefore it can be done reliably in spite
of the monopoles' strong coupling to the electromagnetic field. This article
explains this phenomenon and discusses the bounds on monopole masses arising
from the strongest magnetic fields in the Universe, which are in neutron stars
known as magnetars and in heavy ion collision experiments such as lead-lead
collisions carried out in November 2018 in the Large Hadron Collider at CERN.
It will also discuss open theoretical questions affecting the calculation.
