Elimination of spurious modes within QRPA

TL;DR

This paper introduces a generalized method to eliminate spurious modes in QRPA nuclear excitation calculations, improving accuracy across various symmetry violations and demonstrating effectiveness with Skyrme QRPA on deformed samarium.

Contribution

A unified approach for removing spurious admixtures in QRPA, applicable to multiple symmetry violations and compatible with different calculation levels.

Findings

Successfully reproduces known SA corrections.

Effectively removes spurious modes in deformed nuclei.

Demonstrates improved accuracy in Skyrme QRPA calculations.

Abstract

We suggest a generalized method for elimination of spurious admixtures (SA) from intrinsic nuclear excitations described within the Quasiparticle-Random-Phase-Approximation (QRPA). Various kinds of SA-corrections are treated at the same theoretical ground. The known corrections are well reproduced. As relevant cases, we consider subtraction of SA related with i) violation of the translational invariance (isovector E1 and isoscalar toroidal and compression E1 modes), ii) pairing-induced non-conservation of the particle number (E2(K=0) and E0 modes), and iii) rotational invariance (E2(K=1) and M1(K=1) modes). The SA subtraction can be done at the level of QRPA states, electromagnetic responses, and even transition operators. The additional deformation-induced corrections are proposed. The accuracy of the method is demonstrated by Skyrme QRPA calculations for axially-deformed $^{154}$Sm.