Practicable factorized TDLDA for arbitrary density- and current-dependent functionals

Abstract

We propose a practicable method for describing linear dynamics of different finite Fermi systems. The method is based on a general self-consistent procedure for factorization of the two-body residual interaction. It is relevant for diverse density- and current-dependent functionals and, in fact, represents the self-consistent separable random-phase approximation (RPA), hence the name SRPA. SRPA allows to avoid diagonalization of high-rank RPA matrices and thus dwarfs the calculation expense. Besides, SRPA expressions have a transparent analytical form and so the method is very convenient for the analysis and treatment of the obtained results. SRPA demonstrates high numerical accuracy. It is very general and can be applied to diverse systems. Two very different cases, the Kohn-Sham functional for atomic clusters and Skyrme functional for atomic nuclei, are considered in detail as particular examples. SRPA treats both time-even and time-odd dynamical variables and, in this connection, we discuss the origin and properties of time-odd currents and densities in initial functionals. Finally, SRPA is compared with other self-consistent approaches for the excited states, including the coupled-cluster method.