The Fock representation of the Coulomb interaction. I. Two-body problem
Abstract
In the momentum-space few-body theory of light nuclei, where the Faddeev equations with separable two-body input close on one-variable amplitudes, the unscreened Coulomb interaction is exactly separable by the stereographic projection of Fock, with analytic form factors and strengths, and the truncation of the expansion converges at negative energies. It is derived here as an operator identity for the potential and added, without screening or fitting, as a block of separable terms to the separable nuclear input of a charged pair. The representation is compared with the screening--renormalization method and with Coulomb-distorted form factors on two-body benchmarks: the off-shell t~matrix, the Coulomb displacement of the αp Pauli-forbidden state, and the Coulomb-modified phases of the pp, αp and αα pairs. The Feshbach--Schur projection of the Pauli-forbidden state is shown to require the Coulomb-dressed eigenstate, which the Fock block provides within the same separable problem. At positive energy a finite truncation is a screened Coulomb potential with an analytic, momentum-dependent radius.
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BibTeX
@misc{nishonov2026fock,
title = {{The Fock representation of the Coulomb interaction. I. Two-body problem}},
author = {M. M. Nishonov},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.16585},
eprint = {2609.16585},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.16585},
}
RIS
TY - UNPB
TI - The Fock representation of the Coulomb interaction. I. Two-body problem
AU - M. M. Nishonov
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2609.16585
UR - https://arxiv.org/abs/2609.16585
AB - In the momentum-space few-body theory of light nuclei, where the Faddeev equations with separable two-body input close on one-variable amplitudes, the unscreened Coulomb interaction is exactly separable by the stereographic projection of Fock, with analytic form factors and strengths, and the truncation of the expansion converges at negative energies. It is derived here as an operator identity for the potential and added, without screening or fitting, as a block of separable terms to the separable nuclear input of a charged pair. The representation is compared with the screening--renormalization method and with Coulomb-distorted form factors on two-body benchmarks: the off-shell t~matrix, the Coulomb displacement of the αp Pauli-forbidden state, and the Coulomb-modified phases of the pp, αp and αα pairs. The Feshbach--Schur projection of the Pauli-forbidden state is shown to require the Coulomb-dressed eigenstate, which the Fock block provides within the same separable problem. At positive energy a finite truncation is a screened Coulomb potential with an analytic, momentum-dependent radius.
ER -