Frankfurt 2014 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 39: Struktur und Dynamik von Kernen

HK 39.6: Talk

Thursday, March 20, 2014, 15:30–15:45, HZ 4

Energy-variance extrapolation for importance-truncated no-core and valence-space shell model — •Christina Stumpf, Jonas Braun, Roland Wirth, and Robert Roth — Institut für Kernphysik, Technische Universität Darmstadt

The no-core shell model (NCSM) and valence-space shell model (SM) are successful tools for the description of the nuclear spectroscopy. Both methods are computationally demanding and are limited by the model-space dimensions. To extend the NCSM and SM to larger model spaces, we apply an importance-truncation (IT) scheme based on a perturbative importance measure reducing the model spaces to the relevant basis states for the description of one or a few target eigenstates. This IT scheme necessitates an extrapolation to vanishing importance measure. Since the dependence of the energies on the importance measure can be highly non-linear, the extrapolation can give rise to large uncertainties. We present a more sophisticated extrapolation technique based on the energy variance, which vanishes in the limit of the full model space. We demonstrate the efficiency of the IT-NCSM and IT-SM with energy-variance extrapolation for ground-state and excitation energies of p-shell nuclei (IT-NCSM) and pf-shell nuclei (IT-SM) by comparing the results to both, full and importance-truncated NCSM and SM calculations with the conventional threshold extrapolation.

* Supported by DFG (SFB 634), HIC for FAIR and BMBF (06DA70471)