Construction of the electromagnetic current operator in different forms of Poincaré-invariant quantum mechanics

In an approach of the Poincaré-invariant quantum mechanics in a modified relativistic impulse approximation performed construction of the operator of the electromagnetic current for different forms of dynamics (instant form, point form and dynamics of the light-front). The current operator is constructed according to the conditions of Lorentz covariance and conservation. It is shown that the analytical expressions for the form factor are identical in all forms of dynamics. Numerical calculations of the pion form factor with the wave function obtained by the variational method are in good agreement with experiment.