Electromagnetic interaction in theory with Lorentz invariant CPT violation

An attempt is made to incorporate the electromagnetic interaction in a Lorentz invariant but CPT violating non-local model with particle-antiparticle mass splitting, which is regarded as a modified QED. The gauge invariance is maintained by the Schwinger non-integrable phase factor but the electromagnetic interaction breaks C, CP and CPT symmetries. Implications of the present CPT breaking scheme on the electromagnetic transitions and particle-antiparticle pair creation are discussed. The CPT violation such as the one suggested in this Letter may open a new path to the analysis of baryon asymmetry since some of the Sakharov constraints are expected to be modified.