Symmetry broken and restored coupled-cluster theory: II. Global gauge symmetry and particle number

Thomas Duguet (1, 2, 3) , A. Signoracci (4, 5)

1 DPHN - Département de Physique Nucléaire (ex SPhN)
2 NSCL - National Superconducting Cyclotron Laboratory
3 K.U. LEUVEN - Instituut voor Kern- en Stralingsfysica
4 Department of Physics and Astronomy [Knoxville]
5 Physics Division [Oak Ridge]

We have recently extended many-body perturbation theory and coupled-cluster theory performed on top of a Slater determinant breaking rotational symmetry to allow for the restoration of the angular momentum at any truncation order (T. Duguet, $\it J. Phys. G: Nucl. Part. Phys.$ 42, 025107 (2015). Following a similar route, we presently extend Bogoliubov many-body perturbation theory and Bogoliubov coupled cluster theory performed on top of a Bogoliubov reference state breaking global gauge symmetry to allow for the restoration of the particle number at any truncation order. Eventually, formalisms can be merged to handle $SU(2)$ and $U(1)$ symmetries at the same time. Several further extensions of the newly proposed many-body formalisms can be foreseen in the mid-term future. The long-term goal relates to the $ab\ initio$ description of near-degenerate finite quantum systems with an open-shell character.

Mots clés: near-degenerate finite quantum systems; ab initio many-body methods; symmetry breaking and restoration

Domaines: Physique Nucléaire Théorique [nucl-th]; Physique Quantique [quant-ph]

Thomas Duguet, A. Signoracci. Symmetry broken and restored coupled-cluster theory: II. Global gauge symmetry and particle number. Journal of Physics G: Nuclear and Particle Physics, 2017, 44, pp.015103. ⟨10.1088/0954-3899/44/1/015103⟩. ⟨cea-01511225⟩