In physics, a dyon is a hypothetical particle in 4-dimensional theories with both electric and magnetic charges.
Many grand unified theories predict the existence of both magnetic monopoles and dyons.
[1] He extended the Dirac quantization condition to the dyon and used the model to predict the existence of a particle with the properties of the J/ψ meson prior to its discovery in 1974.
The Witten effect, demonstrated by Edward Witten in his 1979 paper,[2] states that the electric charges of dyons must all be equal, modulo one, to the product of their magnetic charge and the theta angle of the theory.
In particular, if a theory preserves CP symmetry then the electric charges of all dyons are integers.