Though the standard model of electroweak interactions is commonly believed to provide a successful unification of electromagnetic and weak interactions, the approximation in the massless limit and the assumption of massless fermion in this model should be investigated further with rigorousness. Here it will be shown that this approximation violates Lorentz invariance and it is still necessary even with the assumption of a massless fermion and the Higgs mechanism. We conclude that the unification of electroweak interactions is only valid with the assumption of Lorentz violation. |