Eur. Phys. J. A (2020) 56: 268
https://doi.org/10.1140/epja/s10050-020-00276-9

Regular Article – Theoretical Physics

Symmetry conserving coupled cluster doubles wave function and the self-consistent odd particle number RPA

¹ Laboratory of Advanced Materials and Quantum Phenomena, Physics Department, FST, El-Manar University, 2092, Tunis, Tunisia
² ISSATM, Carthage University, Avenue de la République, P.O. Box 77, 1054, Amilcar, Tunis, Tunisia
³ Université Paris-Saclay, CNRS-IN2P3, IJCLab, 91405, Orsay Cedex, France
⁴ Université Grenoble Alpes, CNRS, LPMMC, 38000, Grenoble, France

^* e-mail: mohcen.jemai@issatm.u-carthage.tn

Received: 4 August 2020
Accepted: 7 October 2020
Published online: 21 October 2020

Abstract

Mixing single and triple fermions an exact annihilation operator of the Coupled Cluster Doubles wave function with good symmetry was found in Tohyama and Schuck (Phys Rev C 87:044316, 2013). Using these operators with the equation of motion method the so-called self-consistent odd particle number random phase approximation (odd-RPA) was set up. Together with the stationarity condition of the two body density matrix it is shown that the annihilation conditions allow to reduce the order of correlation functions contained in the matrix elements of the odd-RPA equations to a fully self consistent equation for the single particle occupation numbers. Excellent results for the latter and the ground state energies are obtained in an exactly solvable model from weak to strong couplings.