String-like excitations in quantum electrodynamics

A study is made of the evolution of string-like excitations of the gauge field (exponentials ordered along the contour of integration) in free quantum electrodynamics and in electrodynamics with static sources. It is shown that such excitations are unstable and are transformed after radiation of excess energy into the field of Coulomb sources. These results are compared with calculations in lattice quantum electrodynamics. It is also shown that in this case the strong-coupling method is not suitable for solving the confinement problem.