2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/107309The Hamiltonian theory of a relativistic string is considered in a specific reference frame in terms the diffeo-invariant variables. The evolution parameter and energy invariant with respect to the time-coordinate transformations are constructed, so that the dimension of the kinemetric group of diffeomorphisms coincides with the dimension of a set of variables whose velocities are removed by the Gauss-type constraints in accordance with the second Noether theorem. This coincidence allows us to solve the energy constraint, and fulfil Dirac's Hamiltonian reduction.9 pages, Invited Talk at INTAS Summer School and Conference "New trends in High-Energy Physics" Yalta, Crimea, Ukraine, September 10 - 17, 2005High Energy Physics - Theorytext