On-shell transition of SRG and nuclear systems

TL;DR

This paper investigates how the binding energies of various nuclear systems evolve under the SRG cutoff, revealing an on-shell transition point where three- and two-body contributions relate in a specific ratio, using variational estimates and the Idaho-Salamanca N3LO potential.

Contribution

It introduces a variational approach to analyze the SRG evolution of nuclear binding energies and identifies a critical cutoff where on-shell transition behavior emerges.

Findings

Identification of the SRG cutoff $$ as the on-shell transition point.

At $$, the ratio of three-body to two-body contributions is 1/4.

Binding energies follow generalized Tjon lines during SRG evolution.

Abstract

We make variational estimates for the binding energies of $^2H,~^3H,~^4He,~^{16}O,~^{40}Ca$, showing their running with the Similarity Renormalization Group (SRG) cutoff towards the infrared region and show the generalized Tjon lines that emerge from the calculations. We infer the SRG evolution of the three-body contributions for the $^3H$ and $^4He$ binding energies by computing the two-body contributions with a variational approach assuming that four-body forces are negligible. At any given SRG cutoff, the three-body contributions may then be inferred as being the experimental value minus the two-body contributions. The off-shell / on-shell transition at a critical SRG cutoff $\lambda_c$ drives the behavior of all binding energies and this scale is the turning point of the generalized Tjon lines. Also, at $\lambda_c$ the ratios between three-body and two-body contributions to the binding energies, $B_{\lambda_c}(3) ~/~ B_{\lambda_c}(2)$, are the same in both $^3H$ and $^4He$ systems and equal to $1/4$, so that $B_{\lambda_c}(2) ~=~ 4~B_{\lambda_c}(3)$. All calculations are carried out with the Idaho-Salamanca N3LO potential, which is evolved with the SRG up to the infrared fixed point ($\lambda \to 0$) in all S, P, D, F and G partial-wave channels in order to compute the variational binding energies at several SRG cutoff scales.