Angular-momentum projection in coupled-cluster theory: Structure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Mg</mml:mi><mml:mprescripts/><mml:none/><mml:mn>34</mml:mn></mml:mmultiscripts></mml:math>
G. Hagen, S. J. Novario, Z. H. Sun, T. Papenbrock, G. R. Jansen, Justin G. Lietz, T. Duguet, A. Tichai
Abstract
Single- reference coupled-cluster theory is an accurate and affordable computational method for the nuclear many-body problem. For open-shell nuclei, the reference state typically breaks rotational invariance and angular momentum must be restored as a good quantum number. We perform angular-momentum projection after variation and employ the disentangled coupled-cluster formalism and a Hermitian approach. We compare our results with benchmarks for $^{8}\mathrm{Be}$ and $^{20}\mathrm{Ne}$ using a two-nucleon interaction from chiral effective field theory and for $pf$-shell nuclei within the traditional shell model. We compute the rotational band in the exotic nucleus $^{34}\mathrm{Mg}$ and find agreement with data.