title: High-order variational calculation for the frequency of time-periodic solutions.
abstract: We develop a convergent variational perturbation theory for the frequency of time-periodic solutions of nonlinear dynamical systems. The power of the theory is illustrated by applying it to the Duffing oscillator.
authors.affiliation: Institute of Theoretical Physics, Free University of Berlin, Arnimallee 14, D-14195 Berlin, Germany. pelster@physik.fu-berlin.de
authors.forename: Axel
authors.initials: A
authors.lastname: Pelster
authors.forename: Hagen
authors.initials: H
authors.lastname: Kleinert
authors.forename: Michael
authors.initials: M
authors.lastname: Schanz