Elsevier

Nuclear Physics A

Volume 451, Issue 2, 24 March 1986, Pages 269-298
Nuclear Physics A

Self-consistent medium polarization in RPA

https://doi.org/10.1016/0375-9474(86)90415-XGet rights and content

Abstract

The standard random-phase approximation for finite systems is extended by including the effect of the exchange of the RPA phonons in the residual interaction selfconsistently. It is shown that this particle-hole interaction is strongly energy dependent due to the presence of poles corresponding to 2p2h (and more complex) excitations. The RPA eigenvalue problem with this energy-dependent residual interaction also provides solutions for these predominantly 2p2h-like states. In addition a modified normalization condition is obtained.

This new scheme is applied to 56Ni (56Co) in a large (up to 7ħω) configuration space using a residual interaction of G-matrix type. It is shown that the lowest 2+ eigenvalue, which in the standard RPA becomes imaginary, is stabilized when the selfconsistent screening is taken into account. Another feature observed is the splitting of the M1 strength as an example of 1p1h and 2p2h mixing.

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