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Abstract: Covariant density functional theory, which has so far been applied onlywithin the framework of static and time dependent mean field theory is extendedto include Particle-Vibration Coupling (PVC) in a consistent way. Starting froma conventional energy functional we calculate the low-lying collectivevibrations in Relativistic Random Phase Approximation (RRPA) and construct anenergy dependent self-energy for the Dyson equation. The resultingBethe-Salpeter equation in the particle-hole ($ph$) channel is solved in theTime Blocking Approximation (TBA). No additional parameters are used and doublecounting is avoided by a proper subtraction method. The same energy functional,i.e. the same set of coupling constants, generates the Dirac-Hartreesingle-particle spectrum, the static part of the residual $ph$-interaction andthe particle-phonon coupling vertices. Therefore a fully consistent descriptionof nuclear excited states is developed. This method is applied for aninvestigation of damping phenomena in the spherical nuclei with closed shells$^{208}$Pb and $^{132}$Sn. Since the phonon coupling terms enrich the RRPAspectrum with a multitude of $ph\otimes$phonon components a noticeablefragmentation of the giant resonances is found, which is in full agreement withexperimental data and with results of the semi-phenomenologicalnon-relativistic approach.

Autor: E. Litvinova, P. Ring, V. Tselyaev


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