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Lecture U. von Barth


18 March 2005 FWN-Building 5116.0107, Nijenborgh 4, 9747 AG, Groningen
Speaker:Prof. Dr. U. von Barth
Affiliation:Lund University, Sweden
Title:Successively better and conserving response function within time-dependent density-functional theory obtained from variational many-body theory
Date:Fri Mar 18, 2005
Location:FWN-Building 5116.0107
Host:R. Broer
Telephone:+31 50 363 4374


The traditional approach to the optical response of electronic systems is the computationally demanding Bethe-Salpeter theory. Time-dependent density-functional theory (TDDFT) offers an alternative route toward the same goal but involving much less computational effort. A description within TDDFT requires some knowledge of the so called exchange-correlation kernel for which approximations can be constructed from many-body perturbation theory. A particularly well behaved set of successively better approximations for the kernel is obtained from the variational approach to many-body perturbation theory. The resulting kernels give rise to response functions which obey several experimentally important conservation laws and consistency requirements like, e. the f-sum rule or momentum conservation. Of particular interest to extended Coulombic systems is the version of variational many-body theory referred to as the PSI formalism. This version allows for the use of approximate screening functions leading to a strong reduction of the computational effort in low-symmetry systems. Alternatively, the PSI formalism lends itself to the use of approximate model vertices or particle-hole interactions thereby enabling a more realistic description many-body effects without causing an undue increase of the computational labour.
Last modified:22 October 2012 2.31 p.m.