Toward Scalable Many-Body Calculations for Nuclear Open Quantum Systems using the Gamow Shell Model

TL;DR

This paper introduces a parallelization scheme for the Gamow Shell Model, enabling scalable many-body calculations for weakly bound and resonant nuclear systems at the limits of the nuclear chart.

Contribution

A novel 2D MPI/OpenMP parallelization approach significantly improves the computational efficiency of the Gamow Shell Model for large-scale nuclear physics calculations.

Findings

Enhanced computational capabilities of GSM with the new parallelization scheme

Successful numerical examples demonstrating scalability

Ability to handle larger complex matrices efficiently

Abstract

Drip-line nuclei have very different properties from those of the valley of stability, as they are weakly bound and resonant. Therefore, the models devised for stable nuclei can no longer be applied therein. Hence, a new theoretical tool, the Gamow Shell Model (GSM), has been developed to study the many-body states occurring at the limits of the nuclear chart. GSM is a configuration interaction model based on the use of the so-called Berggren basis, which contains bound, resonant and scattering states, so that inter-nucleon correlations are fully taken into account and the asymptotes of extended many-body wave functions are precisely handled. However, large complex symmetric matrices must be diagonalized in this framework, therefore the use of very powerful parallel machines is needed therein. In order to fully take advantage of their power, a 2D partitioning scheme using hybrid MPI/OpenMP parallelization has been developed in our GSM code. The specificities of the 2D partitioning scheme in the GSM framework will be described and illustrated with numerical examples. It will then be shown that the introduction of this scheme in the GSM code greatly enhances its capabilities.