  Nonperturbative, in inverse Thouless conductance 1/g, corrections to
distributions of level velocities and level curvatures in quasi-one-dimensional
disordered conductors with a topology of a ring subject to a constant vector
potential are studied within the framework of the instanton approximation of
nonlinear sigma-model. It is demonstrated that a global character of the
perturbation reveals the universal features of the level dynamics. The
universality shows up in the form of weak topological oscillations of the
magnitude ~ exp(-g) covering the main bodies of the densities of level
velocities and level curvatures. The period of discovered universal
oscillations does not depend on microscopic parameters of conductor, and is
only determined by the global symmetries of the Hamiltonian before and after
the perturbation was applied. We predict the period of topological oscillations
to be 4/(pi)^2 for the distribution function of level curvatures in orthogonal
symmetry class, and 3^(1/2)/(pi) for the distribution of level velocities in
unitary and symplectic symmetry classes.
