Combining the in-medium similarity renormalization group with the density matrix renormalization group: Shell structure and information entropy

TL;DR

This paper introduces a hybrid computational method combining DMRG and VS-IMSRG to efficiently study nuclear structure, enabling accurate calculations of energies and entanglement in medium-mass isotopes.

Contribution

The paper develops a novel hybrid VS-DMRG framework that improves computational efficiency for large nuclear systems and provides new insights into nuclear correlations and shell structure.

Findings

Successfully computed ground and excited states of nickel isotopes.

Revealed nuclear shell closures and pairing correlations through entanglement measures.

Demonstrated favorable scaling compared to traditional methods.

Abstract

We propose a novel many-body framework combining the density matrix renormalization group (DMRG) with the valence-space (VS) formulation of the in-medium similarity renormalization group. This hybrid scheme admits for favorable computational scaling in large-space calculations compared to direct diagonalization. The capacity of the VS-DMRG approach is highlighted in ab initio calculations of neutron-rich nickel isotopes based on chiral two- and three-nucleon interactions, and allows us to perform converged ab initio computations of ground and excited state energies. We also study orbital entanglement in the VS-DMRG, and investigate nuclear correlation effects in oxygen, neon, and magnesium isotopes. The explored entanglement measures reveal nuclear shell closures as well as pairing correlations.