title: Parametric statistics of individual energy levels in random Hamiltonians.
abstract: We establish a general framework to explore parametric statistics of individual energy levels in disordered and chaotic quantum systems of unitary symmetry. The method is applied to the calculation of the universal intralevel parametric velocity correlation function and the distribution of level shifts under the influence of an arbitrary external perturbation.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom.
authors.forename: I E
authors.initials: IE
authors.lastname: Smolyarenko
authors.forename: B D
authors.initials: BD
authors.lastname: Simons