Effective Lagrangian of QED with a magnetic charge and dyon mass bounds

The effective Lagrangian of QED coupled to dyons is calculated. The resulting generalization of the Euler-Heisenberg Lagrangian contains nonlinear P- and T-noninvariant terms corresponding to the virtual pair creation of dyons. The corresponding P- and T-violating part of the matrix element for light-by-light scattering is considered. This effect induces an electric dipole moment for the electron, of order M-2, where M is the dyon mass. The current limit on the electric dipole moment of the electron yields the lower dyon mass bound M>1 TeV. copyright 1997 The American Physical Society