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تسجيل مستخدم جديدAb Initio Study of 40Ca with an Importance Truncated No-Core Shell Model
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We propose an importance truncation scheme for the no-core shell model, which enables converged calculations for nuclei well beyond the p-shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for 4He and 16O. Then, we present the first converged calculations for the ground state of 40Ca within no-core model spaces including up to 16hbarOmega-excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.
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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.
We respond to Comment on our recent letter (Phys.Rev.Lett.99:092501,2007) by Dean et al (arXiv:0709.0449).
Nuclear structure and reaction theory is undergoing a major renaissance with advances in many-body methods, strong interactions with greatly improved links to Quantum Chromodynamics (QCD), the advent of high performance computing, and improved comput
ational algorithms. Predictive power, with well-quantified uncertainty, is emerging from non-perturbative approaches along with the potential for guiding experiments to new discoveries. We present an overview of some of our recent developments and discuss challenges that lie ahead. Our foci include: (1) strong interactions derived from chiral effective field theory; (2) advances in solving the large sparse matrix eigenvalue problem on leadership-class supercomputers; (3) selected observables in light nuclei with the JISP16 interaction; (4) effective electroweak operators consistent with the Hamiltonian; and, (5) discussion of A=48 system as an opportunity for the no-core approach with the reintroduction of the core.
We present an ab initio approach for the description of collective excitations and transition strength distributions of arbitrary nuclei up into the sd-shell that based on the No-Core Shell Model in combination with the Lanczos strength-function meth
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