Polarization of a vacuum of charged vector mesons by a strong external field

An expression for the contribution to the effective Lagrangian of an electromagnetic field due to the polarization of the vacuum of Weinberg-Salam charged vector bosons by a strong magnetic field is obtained and investigated. It is shown that, within the framework of the linear approximation of the Weinberg-Salam model, there is a threshold of $W^{\pm}$-boson pair creation in a magnetic field.