Topological universality of level dynamics in quasi-one-dimensional disordered conductors

Nonperturbative, in inverse Thouless conductance g(-1), corrections to dist ributions of level velocities and level curvatures in quasi-one-dimensional disordered conductors with a topology of a ring subject to a constant vect or potential are studied within the framework of the instanton approximatio n of nonlinear cr model. It is demonstrated that a global character of the perturbation reveals the universal features of the level dynamics. The univ ersality shows up in the form of weak topological oscillations of the magni tude similar to e(-g) covering the main bodies of the densities of level ve locities and level curvatures. The period of discovered universal oscillati ons does not depend on microscopic parameters of conductor, and is only det ermined by the global symmetries of the Hamiltonian before and after the pe rturbation was applied. We predict the period of topological oscillations t o be 4/pi(2) for the distribution function of level curvatures in orthogona l symmetry class, and root 3/pi for the distribution of level velocities in unitary and symplectic symmetry classes. [S0163-1829(99)02747-2].