Separation of one-pion exchange in the three-nucleon system

Ascertain whether, in the three-nucleon system, the long-range one-pion-exchange interaction can be cleanly separated from short-range interactions—analogous to the separation achieved for nucleon–nucleon scattering within the modified effective-range expansion and the modified Lüscher equation—so as to enable a practical finite-volume treatment for three-body systems.

Background

A central contribution of the paper is a finite-volume reformulation of the modified effective-range expansion that separates known long-range forces from unknown short-range physics in two-body scattering. Extending this separation to three-body systems would be valuable but is nontrivial.

The authors explicitly label as a major challenge the extension to three particles, specifically questioning whether the long-range one-pion exchange can be disentangled from short-range components in the three-nucleon case as neatly as in the two-nucleon case.