Point form relativistic quantum mechanics and electromagnetic form factors

A relativistic quantum mechanics of constituents is formulated in which particles are bound states of a mass operator. The point form of relativistic dynamics is used, in which Lorentz transformations are kinematic, and the four-momentum operator carries all the interactions. A general covariant expression for matrix elements of the electromagnetic current operator is given in which the invariant form factors are reduced matrix elements of the Poincar\'e group. A point form relativistic impulse approximation is formulated, in which invariant form factors of particles are given in terms of their underlying constituents.