Explicit symmetry breaking
An example is the spectral line splitting in the Zeeman effect, due to a magnetic interaction perturbation in the Hamiltonian of the atoms involved.In the latter, the defining equations respect the symmetry but the ground state (vacuum) of the theory breaks it.A system of accelerated charges results in electromagnetic radiation when the geometric symmetry of the electric field in free space is explicitly broken by the associated electrodynamic structure under time varying excitation of the given system.This is quite evident in an antenna where the electric lines of field curl around or have rotational geometry around the radiating terminals in contrast to linear geometric orientation within a pair of transmission lines which does not radiate even under time varying excitation.[2] A common setting for explicit symmetry breaking is perturbation theory in quantum mechanics.The base Hamiltonian might be chosen to provide a starting point close to the system being modelled.