title: Derivative discontinuities in time-dependent density-functional theory.
abstract: Based on the Runge-Gross theorem for ensembles we investigate the influence of particle-number-changes on the exchange-correlation potential in time-dependent density-functional theory. We show that the potential changes discontinuously when the particle number crosses an integer value. Real-time simulations of an atomic ionization process demonstrate that this discontinuity appears naturally in the theory of the time-dependent optimized effective potential. The importance of such a discontinuity for physical processes, even such ones in which the particle number is a constant, is discussed.
authors.affiliation: Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Mundt
authors.forename: Stephan
authors.initials: S
authors.lastname: Kümmel