In-Medium Similarity Renormalization Group Approach to the Nuclear Many-Body Problem

TL;DR

This paper explains the In-Medium Similarity Renormalization Group (IMSRG) method for solving complex nuclear many-body problems, demonstrating its effectiveness through applications to models and neutron matter, and comparing it with other advanced methods.

Contribution

It provides a comprehensive pedagogical overview of IMSRG, including formalism, numerical implementation, and applications to nuclear physics problems, highlighting its advantages and future directions.

Findings

IMSRG effectively decouples ground states from excitations

Results agree with Coupled Cluster and Green's Function methods

Demonstrates applicability to neutron matter and pairing models

Abstract

We present a pedagogical discussion of Similarity Renormalization Group (SRG) methods, in particular the In-Medium SRG (IMSRG) approach for solving the nuclear many-body problem. These methods use continuous unitary transformations to evolve the nuclear Hamiltonian to a desired shape. The IMSRG, in particular, is used to decouple the ground state from all excitations and solve the many-body Schr\"odinger equation. We discuss the IMSRG formalism as well as its numerical implementation, and use the method to study the pairing model and infinite neutron matter. We compare our results with those of Coupled cluster theory, Configuration-Interaction Monte Carlo, and the Self-Consistent Green's Function approach. The chapter concludes with an expanded overview of current research directions, and a look ahead at upcoming developments.