Quantum-electrodynamic model of the finite-size electron and calculation of the fine-structure constant

We propose a model of a relativistic string formed by a scalar complex field, acting as electromagnetic field source. An axiosymmetric solutions of the stationary equations for the scalar and electromagnetic fields are found numerically. The mass $m$ is calculated as a function of the charge $e$ and the magnetic moment $\mu$ of the system. The resulting toroidal structure is interpreted as an electron because the calculated ratio $e^3/(2mc^2\mu)$ coincides with the fine-structure constant $\alpha=e^2/(\hbar c)\approx e^3/(2m_ec^2\mu_e)$.