Hamiltonian of null strings. An invariant action of null (super)membranes

A new action functional with linear velocity dependence is suggested for describing the Schild strings. A Hamiltonian formalism for null strings is constructed. The second class constraints have been solved. A new effective action functional and a Hamiltonian of null strings, which generalize the action and Hamiltonian for a lightlike particle, are derived. Models of null superstrings and null (super)membranes and invariant formulations of their action functionals are suggested