Datensatz

Zusammenfassung

Ab initio nuclear many-body frameworks require extensive computational
resources, especially when targeting heavier nuclei. Importance-truncation (IT)
techniques allow to significantly reduce the dimensionality of the problem by
neglecting unimportant contributions to the solution of the many-body problem.
In this work, we apply IT methods to the nonperturbative in-medium similarity
renormalization group (IMSRG) approach and investigate the induced errors for
ground-state energies in different mass regimes based on different nuclear
Hamiltonians. We study various importance measures, which define the IT
selection, and identify two measures that perform best, resulting in only small
errors to the full IMSRG(2) calculations even for sizable compression ratios.
The neglected contributions are accounted for in a perturbative way and serve
as an estimate of the IT-induced error. Overall we find that the IT-IMSRG(2)
performs well across all systems considered, while the largest compression
ratios for a given error can be achieved when using soft Hamiltonians and for
large single-particle bases.