In the past decade, coupled-cluster theory has seen a renaissance in nuclear physics, with computations of neutron-rich and medium-mass nuclei. The method is efficient for nuclei with product-state references, and it describes many aspects of weakly
bound and unbound nuclei. This report reviews the technical and conceptual developments of this method in nuclear physics, and the results of coupled-cluster calculations for nucleonic matter, and for exotic isotopes of helium, oxygen, calcium, and some of their neighbors.
We review some applications of self-consistent Greens function theory to studies of one- and two-nucleon structure in finite nuclei. Large-scale microscopic calculations that employ realistic nuclear forces are now possible. Effects of long-range c
orrelations are seen to play a dominant role in determining the quenching of absolute spectroscopic factors. They also enhance considerably (e,epn) cross sections in superparallel kinematics, in agreement with observations.
This article presents several challenges to nuclear many-body theory and our understanding of the stability of nuclear matte r. In order to achieve this, we present five different cases, starting with an idealized toy model. These cases expose proble
ms that need to be understood in order to match recent advances in nuclear theory with current experimental programs in low-energy nuclear physics. In particular, we focus on our current understanding, or lack thereof, of many-body forces, and how they evolve as functions of the number of particles . We provide examples of discrepancies between theory and experiment and outline some selected perspectives for future research directions.
The single-particle spectral function of 56Ni has been computed within the framework of self-consistent Greens functions theory. The Faddeev random phase approximation method and the G-matrix technique are used to account for the effects of long- and
short-range physics on the spectral distribution. Large scale calculations have been performed in spaces including up to ten oscillator shells. The chiral N3LO interaction is used together with a monopole correction that accounts for eventual missing three-nucleon forces. The single-particle energies associated with nucleon transfer to valence 1p0f orbits are found to be almost converged with respect to both the size of the model space and the oscillator frequency. The results support that 56Ni is a good doubly magic nucleus. The absolute spectroscopic factors to the valence states on A=55,57 are also obtained. For the transition between the ground states of 57Ni and 56Ni, the calculations nicely agree with heavy-ion knockout experiments.
In a recent Letter [Phys. Rev. Lett. 99, 092501 (2007)], Roth and Navratil present an importance-truncation scheme for the no-core shell model. The authors claim that their truncation scheme leads to converged results for the ground state of 40-Ca. W
e believe that this conclusion cannot be drawn from the results presented in the Letter. Furthermore, the claimed convergence is at variance with expectations of many-body theory. In particular, coupled-cluster calculations indicate that a significant fraction of the correlation energy is missing.
