Antisymmetrized, translationally invariant theory of the nucleon optical potential

TL;DR

This paper develops a translationally invariant, antisymmetrized theoretical framework for the nucleon optical potential, avoiding mean-field assumptions, and connects it with established models like Feshbach's projection approach.

Contribution

It introduces a new, fully translationally invariant operator-based formulation of the nucleon optical potential that incorporates exchange mechanisms without mean-field references.

Findings

Optical potential operator satisfies rotational and translational invariance.

Reduces to Feshbach's formulation in the weak-binding limit.

Provides definitions for nucleon Green's function and Dyson self-energy with translational corrections.

Abstract

Earlier work showed how a nucleon optical model wave function could be defined as a projection of a many-nucleon scattering state within a translationally invariant second quantised many-body theory. In this paper an optical potential operator that generates this optical model wave function is defined through a particular off-shell extension of the elastic transition operator. The theory is express explicitly in terms of the many-nucleon Hamiltonian in a mixed representation in which localised target nucleus states feature. No reference to a mean-field concept is involved in the definition. It is shown that the resulting optical model operator satisfies the requirements of rotational and translational invariance and has standard behaviour under the time reversal transformation. The contributions to the optical potential from two different exchange mechanisms are expressed in terms of an effective Hamiltonian involving a nucleon-number conserving one-body interaction. In the weak-binding limit the method reduces to a a version of Feshbach's projection operator formulation of the optical potential with a truncated nucleon-nucleon potential including exchange terms and recoil corrections. Definitions of the nucleon single-particle Green's function and the corresponding Dyson self-energy modified by corrections for translational invariance are presented and different definitions of the optical potential operator are compared.