On retardation effect in the formfactor of two-particle bound state

In the Logunov–Tavkhelidze quasipotential approach the convergence of the iteration procedure corresponding to the account of the dynamical retardation effect in the electromagnetic formfactor of the two scalar particle bound state with the separable Bethe–Salpeter kernel is investigated. The status of the relativistic momentum approximation within the framework of this approach is discussed. In the static approximation the electromagnetic vertex operator obeying the current conservation and normalization conditions is constructed with regard to the interaction current. The comparative analysis of the formfactor in the different approximations is done.