In-Medium Similarity Renormalization Group for Nuclei

TL;DR

This paper introduces an in-medium similarity renormalization group (IM-SRG) method for nuclear structure calculations, enabling efficient and accurate ab-initio computations of nuclear ground states by evolving Hamiltonians directly within the nucleus.

Contribution

The paper develops a novel in-medium SRG approach that simplifies many-body nuclear calculations by evolving Hamiltonians within the nucleus using two-body operators, improving accuracy and efficiency.

Findings

Accurately computed ground-state energies for $^4$He, $^{16}$O, and $^{40}$Ca.

Method achieves accuracy comparable to coupled-cluster calculations.

Demonstrates nonperturbative evolution of nuclear Hamiltonians in medium.

Abstract

We present a new ab-initio method that uses similarity renormalization group (SRG) techniques to continuously diagonalize nuclear many-body Hamiltonians. In contrast with applications of the SRG to two- and three-nucleon interactions in free space, we perform the SRG evolution "in medium" directly in the $A$-body system of interest. The in-medium approach has the advantage that one can approximately evolve $3,...,A$-body operators using only two-body machinery based on normal-ordering techniques. The method is nonperturbative and can be tailored to problems ranging from the diagonalization of closed-shell nuclei to the construction of effective valence shell-model Hamiltonians and operators. We present first results for the ground-state energies of $^4$He, $^{16}$O and $^{40}$Ca, which have accuracies comparable to coupled-cluster calculations.