  On the basis of the relativistic symmetry of Minkowski space, we derive a
Lorentz invariant equation for a spread electron. This equation slightly
differs from the Dirac equation and includes additional terms originating from
the spread of an electron. Further, we calculate the anomalous magnetic moment
based on these terms. These calculations do not include any divergence;
therefore, renormalization procedures are unnecessary. In addition, the
relativistic symmetry existing among coordinate systems will provide a new
prospect for the foundations of quantum mechanics like the measurement process.
