A complex integration technique to remove spurious states associated with spontaneously broken symmetries in RPA calculations

The removal of the spurious states associated with the violation of rotatio nal and gauge invariance by mean field approximation from the RPA solutions describing the low-energy spectrum of nuclei is a notoriously difficult ta sk, in particular in a rotating frame. A novel, numerically accurate yet te chnically simple method to accomplish this aim has been developed based on linear response theory. The results of calculations carried out for the def ormed, superfluid, rotating nucleus Yb-168 testify to the power of the tech nique, the associated solutions respecting the variety of sum rules require d to be fulfilled by the RPA solutions because of conservation laws. (C) 19 99 Elsevier Science B.V. All rights reserved.