Variational and parquet-diagram calculations for neutron matter. II. Twisted Chain Diagrams

TL;DR

This paper introduces a microscopic method to analyze strongly interacting nuclear systems with different spin states, emphasizing the importance of non-parquet diagrams in accurately capturing short-distance many-body effects.

Contribution

It identifies and incorporates non-parquet diagrams into variational calculations for neutron matter, highlighting their significance over other effects at short distances.

Findings

Non-parquet diagrams significantly affect short-distance interactions.

Commutator contributions are crucial when spin-dependent interactions differ greatly.

The method improves the understanding of many-body effects in nuclear systems.

Abstract

We develop a manifestly microscopic method to deal with strongly interacting nuclear systems that have different interactions in spin-singlet and spin-triplet states. In a first step we analyze variational wave functions that have been suggested to describe such systems, and demonstrate that the so-called commutator contributions can have important effects whenever the interactions in the spin-singlet and the spin-triplet states are very different. We then identify these contributions as terms that correspond, in the language of perturbation theory, to non-parquet diagrams. We include these diagrams in a way that is suggested by the Jastrow-Feenberg approach and show that the corrections from non-parquet contributions are, at short distances, larger than all other many-body effects.