Studying short-range correlations and momentum distributions with unitarily transformed operators

TL;DR

This paper investigates short-range correlations in helium-4 using many-body wave functions and the similarity renormalization group, analyzing effects in coordinate and momentum space and assessing the impact of missing higher-body contributions.

Contribution

It applies the SRG to evolve interactions and operators in the no-core shell model, providing insights into short-range correlations and the significance of higher-body effects.

Findings

SRG evolution affects two-body densities in coordinate and momentum space.

Comparison with exact results highlights the impact of missing three-body contributions.

Results demonstrate the importance of including higher-body effects for accurate correlations.

Abstract

Short-range correlations in 4He are investigated using many-body wave functions obtained in the no-core shell model. The similarity renormalization group (SRG) is used to evolve the Argonne V8' interaction and the density operators. The effects of short-range correlations are reflected in the two-body densities in coordinate space as a function of the distance between two nucleons, or alternatively in in momentum space as function of the relative momentum between two nucleons. The SRG transformation is performed in two-body approximation. The importance of missing three-body and higher-body contributions is investigated by comparing results obtained for different flow parameters and by comparing to exact results with the bare Argonne V8' interaction obtained in the correlated Gaussian approach.